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AQUARIUM LIGHTING, Complete Facts & Information
Kelvin, Nanometers, PAR, PUR, Reef, Freshwater Plant & more

This is an depth aquarium lighting article with both basic and advanced applications that is regularly updated, thorough/regular reading is recommended
INDEX
Including These Sections (which can be clicked on to "jump to")
  1. Aquarium Lighting Basics
  2. Kelvin Rating
  3. Nanometer Range (Spectrum)
  4. Lux
  5. PAR (Photosynthetically Active Radiation)
  6. Measuring PAR
  7. Useful Light Energy (PUR)
  8. Lumens
  9. Watts
  10. CRI
  11. Aquarium Light Type
    1. T-2
    2. T- 5
    3. T-12 & T8
    4. CFL
    5. SHO
    6. VHO
    7. Metal Halide
    8. LED
    9. Lunar (Moon Lights)
    10. Induction
    11. HID Xenon etc.
  12. Parameters
  13. Watts Per Gallon Comparison
  14. Light on time & change
  15. Lamp placement
  16. Specimen Placement
  17. Tank Set Up Suggestions
  18. PDF Download
  19. Summary
  20. References

Related Information/ Products
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AQUARIUM LIGHTING
By Carl Strohmeyer
Updated 1/16/12
 

OVERVIEW

When choosing your aquarium lighting (especially Reef or Planted Freshwater), there is much more to consider than watts per gallon.

In fact is the 2-5 watts per gallon 'rule' is a VERY basic start (this rule varies depending upon what is kept & who you ask), however this is very general and quite out-dated due to the variety available modern lights with varying lumens per watt lights, different wavelength, focused lumens, PAR/PUR output, etc.

Sadly the watts per gallon "rule" for aquarium lighting is still thrown around today despite all the technological advances in lighting which often makes this grossly inaccurate.
As an example, a high PAR/PUR LED from the most exclusive/best emitter bins can only need 4% of the wattage as a household T12 to produce the same results (about 15% for better aquarium T8 or T12 lamps), but even then many LEDs available such as those sold by mass merchandisers are not of high useful PAR output (PUR), as these often use much lower quality emitters with poor PUR output.


Please read the full article here to understand why the Watts per gallon is only part of the equation for your aquarium light determination.

As you will read more later in this article a watt is simply a measurement of energy NOT light output or even quality. Even comparable lumen output at the lamp is no longer a good measure of lighting parameter performance due to PAR, PUR, focus, and restrike; as noted earlier a good example is a modern LED (such as the Aqua Ray) which has a vastly higher PUR output than a comparable wattage CFL.

There are other factors effecting lighting for your aquarium than just watt output. For example: You cannot compare the output of a 150 watt Metal Halide to a 150 watt outdoor floodlight. Nor an 85 watt standard incandescent to a 85 Watt 6400 K SHO Bulb. What I am trying to say is sometimes it comes down to comparing apples to oranges.

Other aquarium lighting considerations besides energy used (watts) are PUR, PAR, Lumens per watt and even output relative to the size of the light. For example a SHO that uses 105 watts yet is only 10" and placed into a reflector will be very efficient as per wattage and space utilized for this. Another example is a T-2 bulb that only takes up a small space (7 mm diameter) can be a very productive bulb as per lumens per watt (73 lumens per watt!), PAR and space used.

For example I would recommend a pair of 19 inch/13 watt/ 6400K T-2 lights over a pair of 20 inch/15 watt standard (T8 or T12) for a 20 gallon planted tank; the reasons are higher lumens per watt (73 vs. 40-50) and correct temperature/PAR (6400 K vs. 2100 -4500).
The actual useful energy output of this comparison would be a minimum of 50% more useful energy for roughly the same wattage and same length of lamps

Water penetration is another consideration, as higher frequency "red" light energy is quickly filtered out in water, and many light energy requiring plants, corals, etc. have adapted to light energies found at certain depths of water.

This overview is just an brief explanation, please read further for more in depth discussion (and I do not assume this article is the end all of aquarium lighting discussion, I will add a lot more as time goes on as newer information that explains or corrects the subjects contained in this article better).

It is important to note that Aquarium Lighting is complex subject, and this article has both more depth information as well as some basics (in the summary recommendations), however this is a subject that simply reading one section of this article will yield incomplete information. For this reason I recommend reading the whole article (as well as links provided) for a more thorough understanding (it may take more than one reading as well)
I should also note that while I have years of hands on experience (over 30+), this is a fast evolving subject of aquarium keeping requiring my constant research and consulting with others (who often have more scientific expertise than myself); the result is constant changes to this article.


The five most important criteria in determining the light you need are:
• Lumens per watt
• Lumen focus (as well as restrike)
• PAR (this is important to understand)
• PUR/Useful Light Energy (Probably the most important factor; this is related to PAR, however many lamps can have reasonable PAR output but fail in comparison when PUR is considered).
• Watts (or watts per gallon, however this term is over used/simplistic)

However the above five aquarium lighting criteria is an over simplification, so an understanding as best possible of other aspects as well as the positives and negatives of each lighting type, including types that the often "5-10 years behind technology aquarium industry" ignore such as LED, SHO, T2, or Induction are important as well (as I see it from tests and research; the SHO, T2 and especially the LED are future of aquarium lighting, not the popular dual CFL & others).


Here are other important factors;

1: KELVIN RATING (such as 10,000K daylight bulb):

What is meant with Kelvin Temperature of Lights is not the classic interpretation of what Kelvin is, however I think is should be considered before I move on to our lighting definition of "Kelvin Temperature".

Here is a brief description of Kelvin:
Kelvin is defined by two points: absolute zero, and the triple point of pure water. Absolute zero is defined as being precisely 0 K and –273.15 °C. Absolute zero is where all kinetic energy (motion) in the particles comprising matter ceases, and they are at complete rest. At absolute zero there is NO heat energy (the total absence of heat).
The triple point of water is defined as being 273.16 K and 0.01 °C.

Here are a few Kelvin numbers:
*Absolute zero = 0 K (-273.15C)
*Waters freezing point = 273.15 K (0 C)
*Waters boiling point = 373.1339K (100C)
The true definition of Kelvin is that it is a unit of measure of temperature on the thermodynamic (absolute) temperature scale.

Light Kelvins
Kelvin is used in the lighting industry to define the Color temperature of a bulb. Higher color temperature lamps above 5500 K are "cool" (green–blue) colors, and lower color temperature lamps below 3000 K are "warm" (yellow–red) colors.

Kelvins as applied to color temperature of lights/lamps are derived from the actual temperature of a black body radiator, which is the concept of color temperature based on the relationship between the temperature and radiation emitted by a theoretical standardized material and termed a "black body radiator". This is where the "classic" definition of Kelvin and that used for lights come together, as hypothetically, at cessation of all molecular motion (the black body state of this hypothetical radiator), the temperature is described as being at absolute zero or 0 Kelvin, which is equal to -273 degrees Celsius.
See the picture example below:

Black Body Radiator, Kelvin Color Temperature

An incandescent filament is very dark, and approaches being a black body radiator, so the actual temperature of an incandescent filament is somewhat close to its color temperature in Kelvins.

Incandescent lamps tend to have a color temperature around 3200 K, but this is true only if they are operating with full voltage. When a lamp is dimmed below its full potential, its filament is not as hot, and it produces less light. The reduced temperature of the filament also reduces the color temperature downward. An incandescent light dimmed to 10% is considerably more red in color than one at 100%.

Another consideration as to the color temperature as applied to lights; color temperature does not take into consideration the spectral distribution of a visible light source. In cases where a light source, such as a fluorescent lamp, arc-discharge burner, laser, or gas lamp, does not have a spectral distribution similar to that of a black body radiator.

A few notes about Kelvin:

* Plant chlorophyll absorbs light at wavelengths of 300 to 700 nm (a Kelvin rating of about 6400 strikes a good balance here, which is why this is the best Kelvin temperature for freshwater plants and symbiotic zooxanthellae in corals).
* The lower the "K", the more yellow, then red the light appears, such as a 4500 K bulb.
* The higher the "K", the bluer the light appears, such as a 20,000 K bulb.
*Higher Kelvin Color Temperature lights penetrate water more deeply, even more so in saltwater, however there is less of the infrared "PAR spike" as well.
* The human eye sees mostly sees light around 5500K.
* Candle flame = 1850 – 1900 K
* Sunlight (1 hour after dawn) = 3500 K
* Typical summer light (sun + sky) = 6500 K
* Cool white fluorescent = 4200 K

*Different nanometer wavelengths can be used to reach the same Kelvin Temperature; just as 4+5 & 1+8 both equal 9, so can different nanometer wavelengths be used for the same Kelvin Temperature. This is why often comparing one 6500K lamp to another can often be "apples to oranges" as for necessary useful light energy (PUR) needed by plants or corals

What Kelvin rating for Plants & Corals;

Here are some observations made by me and others in the professional aquarium maintenance community, some of these are simple observations, while others were based on more controlled tests.

*The 6500 Kevin lamps have produced the best freshwater plant growth (as this Kelvin lamp generally has more of the infrared nm spike needed by "higher" plants, but still has some of the 425-500 nm blue).

This Kelvin Lamp can also work with SPS, LPS placed high in the tank water column (nearest the lights) based on the symbiotic zooxanthellae needs found in these corals. For more depth penetration (& to aid in the first blue spike in PAR, please see PAR section), blue actinic, 50,000 K/Actinic or adjustable/multiple LED can be added (such as AquaBeam Marine Blue) can balance out 6500K lamp if used in marine reef tanks.
Please note that saltwater absorbs slightly more light energy than freshwater due to the higher density of the water, so 6500 will not penetrate as deeply and are not a good choice for depths over 12 inches despite some Reef Lights such as the "AI Sol LED" utilizing this Kelvin Temperature output in their reef lights.

*The 9000-10,000 Kelvin lamps also achieve good growth rates, although slower than the 6500 K bulbs in shallow aquariums. 9000 to 10000K bulbs have produced excellent growth with soft corals and LPS, although slower paced SPS growth.
The 10,000K can be a good choice for achieving PAR for better depth penetration than a 6500K bulb (such as 12-20 inch or even deeper aquarium)

*The 14,000K light/lamp (often popular with Metal Halide and LEDs), will penetrate even more than the 10,000K light while still providing useful PAR (this would be the highest "Daylight" Kelvin temperature I would recommend and still expect good growth in corals, see PAR section). An excellent daylight color for tanks between 15 and 30 inches in depth.

*The 20,000 K light/lamp is more blue yet and brings out all of the fluorescent pigments in many corals (making for a very nice appearance). However the many tests and observations show that when used alone except in tanks over 24 inches, the growth rate of SPS corals can come be slowed or even come to a standstill with 20,000 K lamps. Although a good supplement for appearance and deep tanks, these bulbs generally should not be used as the only reef Kelvin temperature in tanks under 24 inches.

*The 50,000K is generally the Kelvin rating of an actinic blue light source which is beneficial for the first "spike" in PAR. This temperature light (as with 20,000K) is best used with other light Kelvin Temperatures and is a better choice than the 20,000K light for such combinations. The 50,000K is a good compliment to the 6500, 10,000, 14,000 Kelvin lights, especially for zooanthellic algae necessary for stony corals, clams, nudibranch, anemones, and other sessile species.


Here is a quote as per their experience with Kelvin Temperature for a freshwater Planted aquarium:

"I had a 175, 6700K Metal Halide over my 22gallon cube, and then switched it over to a 14K bulb I had when I used to do saltwater just to see the difference. I didn't like the blue appearance nor how it made the plants look odd. True, my neon tetras glowed more blue as did my beta, but the plants looked weird. I went back to the 6700K last night to make my final decision. Everything looked much better under that light. It is under 6700K that I got explosive growth when I added a good, CO2 reactor.
After I switched back to the 6700K, my plants were pearling away, and they had their true colors and natural look again! If I decide down the road to change to a saltwater fish only with live rock, I can still use the 6700K lights (I won't go back to raising corals - it was good experience, but in all honesty, I found it boring). People need to use the proper spectrum - they shouldn't use what pleases them; they must use what pleases what you are trying to grow/raise be it fish, corals, or plants. You become the shepherd so tend your flock accordingly (corny but true)."
Gary Sanders

Simple Basic Kelvin Temperature Comparison Test:

First this test is quite accurate when comparing "apples to apples", in other words one 6500K CFL to another.
Simply provide a "control" light such as a new CFL, SHO, T2, T5 with the SAME Kelvin rating. Then use a clean plain piece of white computer printer paper and shine the light through this paper.
The results should provide obvious degradation of light color (often less blue since this is often a nanometer color to go first). This can also be used for comparison of LEDs, SHO, T%, etc where a light (even if new) is suspected of not producing the correct color.
This test is very accurate for the above use, but CANNOT show what light energy wave lengths that go into the kelvin temperature and is not accurate for comparing (as an example) a T2 6500K to a 6500K LED (although it can make for interesting comparisons between different lights and even different Kelvin lights).

Kelvin summary
The Kelvin rating is another area of comparing apples to apples in lights, not just watts. Although the above is a simplified explanation of Kelvin as it applies to lights; as such you cannot compare a 6400 K T8 light to a 6400 MH light (the MH is going to have much more output as you will read later).

However (using a CFL as an example, this can apply to any light type), a 6400K CFL will have a higher useful energy output than a 3500K CFL, this is why an incandescent filament is very low in Kelvin (dark) as derived from the actual temperature as it is just above a black body radiator.
This does not mean that a certain Kelvin bulb is necessarily "better" as factors such as "lumens per watt", watts, focused lumens and especially PAR/PUR MUST be considered as well.

References:
http://micro.magnet.fsu.edu/primer/java/colortemperature/index.html Color Temperature in a Virtual Radiator- This is an interesting resource with a virtual radiator worth checking out. We have currently disabled this link as it is crashing our browsers, once we determine it is working.

http://www.uky.edu/~jholl2/technology_pdfs/KelvinColorTemperature.pdf

http://www.sizes.com/units/color_temperature.htm Back To Top





2: THE NANOMETER RANGE (SPECTRUM)

Visible Light Spectrum

A nanometer scale is used to measure the wave length of light energy from cosmic rays to radio waves. An actinic bulb will have a Nanometer spike at about 420nm, a UVC bulb about 265nm, and a daylight bulb about multiple spikes from 400 to 700nm.
The difference in the wavelength determines how the wave affects its surroundings. It is this wavelength difference that allows short-wave x-ray to pass through walls, while longer-wave visible light cannot pass though the same material; short-wave ultraviolet and x-ray can destroy DNA in living microorganisms and breakdown organic material while visible light will not. All light energy is measured on a "nanometer" (nm) scale. Nanometer means one-billionth of a meter.

This applies to aquariums when we consider the light spectrum and how it applies to our aquariums individual needs: Red light is the first to be filtered out and can only penetrate a short distance. As light waves penetrate deeper into the water, orange and yellow are lost next. Of all the colors of the spectrum blue light penetrates the deepest. Corals need intense equatorial UVA (actinic) as well as other aspects of PAR. Most higher plants need a balanced PAR/PUR light range which includes the blue and two red spikes required for photosynthesis (see section about PAR & PUR).
The Nanometer scale and Kelvin temperatures come together when applied to aquarium lighting this way; Natural sunlight on a clear day registers at 5500- 6500 Kelvin degrees. Kelvin temperatures less than 5500K become more red and yellow and the higher the Kelvin temperature the more blue the light is.

Most photosynthetic invertebrates should be kept with lamps of a daylight Kelvin temperature from 6400-14,000 K (higher Kelvin with deeper specimen placement, not necessarily tank depth). 20,000K daylight lamps can also be used for deeper tanks, however I have found it better to use a 14,000K Daylight or less supplemented with more blue (400nm- 550nm).
Photosynthetic invertebrates (many corals, anemones, clams, nudibranch, etc.) also need more blue (400-550nm) than "higher" plants especially as tanks increase in depth, with 465-485 recently being shown the optimum blue. Not only is blue/actinic lighting beneficial to photosynthetic invertebrates, it is also aesthetically pleasing to the eye when used to supplement "daylight" lighting.

Freshwater aquarium plants benefit from lighting with a Kelvin temperature in the range of approximately 6500 degrees. Freshwater plants prefer light with more red in the spectrum (see PAR Section).


It is noteworthy that Fluorescent and even more so incandescent lights produce a lot of yellow and green nanometer light, which research indicates is mostly wasted energy in terms of the needs or freshwater plants and SPS Corals. This is where an LED Aquarium Light, Metal Halide, or even (to a lesser degree) T2 Lights excels as there is much less wasted yellow/green light.

See the picture to the left that shows a T8 5500 daylight aquarium light that is commonly sold, this graph clearly shows the wasted green/yellow energy as well as the incorrect spike in orange rather than the correct PAR spike in red 630+ nm (click to enlarge)

It is also noteworthy that many "terrestrial plant lights" as well as many aquarium plant lights (often are lower in kelvin temperature) have more "red nanometer spikes" than higher kelvin 6500k, 10,000k & higher lamps.
The problem with these lights is that while all plants utilizing photosynthesis require the same essential ABCs of PAR (see the PAR section), the facts of light energy penetrating water requires higher kelvin (6500k +) be added to provide maximum PUR (see Useful light energy/PUR section). Aquatic Plants and corals have adapted/evolved to the natural light energy at certain depth of water and the misguided attempt to adapt these terrestrial plant lights is not going to be 100% effective as a light with more water penetrating blue & slightly lower red nm energy.



3: LUX:

A measure of the intensity of light (referred to the photometry of light), one lux is equal to one lumen per square meter. Once again this is another area of comparing apples to apples in lights, not just watts.
It is noteworthy that a LUX Reading ONLY reports light intensity to which the human eye is most sensitive (green light)

However this can still be a useful tool for freshwater plants & most corals in marine reef aquariums.
When the Lux is not enough the zooxanthellae (inside of corals tissues) do not create plentiful oxygen.
The minimum light intensity should be no less than 3,000-lux when it reaches the deepest part of the aquarium. You can over light your coral to a light saturation point (quite hard in my experience, but this should be noted), maximum Lux should be no more than 100,000 to 120,000.
By comparison Lux in tropical reefs has been measured to be between 110,000 and 120,000 Lux at the surface of the reef and 20,000-25,000 Lux one meter below the surface.
Back To Top


4: PAR:

PAR is one of the more important considerations along with the even MORE important related Useful Light Energy (aka PUR which literally stands for Photosynthetically Useful Radiation). I have noticed that PAR is both over looked & over-rated (meaning PUR is more important) by both marine and freshwater plant keeping aquarists.

PAR is the abbreviation for Photosynthetically Active Radiation which is the spectral range of solar light from 400 to 700 nanometers that is needed by plants & symbiotic zooanthellic algae (Zooxanthellae are single-celled plants that live in the tissues of animals such as corals, clams, anemones, & nudibranchs) for photosynthesis.
In particular, this is found from actinic UVA to infrared. UVA is 400-550nm (of which 465-485 has the highest PAR of the actinic range) which is the absorption bandwidth of chlorophylls a, c˛, and peridinin (the light-harvesting carotenoid, a pigment related to chlorophyll). Low (near) Infrared is 620-720nm which is the red absorption bandwidth of chlorophylls a and c˛. (I should note for the technical "purists" that might read this article, true infrared is beyond 750 nm, but as per my many resources the energy spikes in the red spectrum are generally referred to as infrared or near infrared)

Photons at shorter wavelengths (UVC) tend to be so energetic that they can be damaging to cells and tissues; fortunately they are mostly filtered out by the ozone layer in the stratosphere. Green light occupies the middle spectrum (550-620nm; what is mostly visible to us) and is partly why chlorophyll is green due to the reflective properties.

Bulbs that emit mostly actinic light will have a lower PAR (although actinic UVA still occupies an spike in PAR as seen from the graph and improves the PAR of your lighting), bulbs that occupy mostly the middle spectrum (yellow-green) such as "warm White (2700- 3500K ) will produce little necessary PAR, while bulbs that produce mostly infrared (as seen from the graph) will produce more important PAR light energy, however it is the balance of infrared and UVA that will generally provide your best PAR output.


PAR, photosynthetic active radiation graphImportant Definitions as it applies PAR in plants and zooanthellic algae: See the graph to the left as it corresponds to each of these definitions.

*A: Phototropic response; having a tendency to move in response to light. Basically this is the Chlorophyll containing plant or algae "moving" to respond to a positive light source to begin the process of photosynthesis (initial growth of plants, zooxanthellae, etc.). This is found in the 420-500nm "blue" spectrum.

*B: Photosynthetic response; the process which begins when energy from light is absorbed by proteins called photosynthetic reaction centers that contain chlorophylls.

*C: Chlorophyll synthesis is the chemical reactions and pathways by the plant hormone cytokinin soon after exposure to the correct Nanometers wave length (about 670 NM) of light resulting in the formation of chlorophyll, resulting in continued growth of a plant, algae, zooxanthellae and the ability to "feed" & propagate, and without this aspect PAR (670 NM light energy), zooxanthellae and plants cannot properly "feed" propagate. The results of the lack of this high PAR "spike" would be stunted freshwater plant growth, and eventually poor coral health in reef tanks. This lack of near-red light over 630nm is common to many so-called aquarium lights (such as the diagram at the bottom of the Nanometers section).

*With this in mind and based on better funded tests/studies outside the aquarium industry show that many stony corals, clams, and other sessile species that depend on photosynthesis of zooanthellic algae not only thrive but also propagate with light that achieves the optimum PAR, which includes daylight from as low as 6500k.
When the amount of energy used (in watts) is considered, this can include 6400 SHO lamps which can generally penetrate most freshwater tanks well and also perform well in marine reef tanks under 18 inches of depth when balanced with blue/actinic lights necessary for the higher need of 465-485nm light energy by symbiotic zooanthellic algae).


Further PAR Information;
As the reader here can see, there are three main spikes in the PAR spectrum, with all three being important, however the most important spikes occur at the red side and all three are generally incorporated more or less in a daylight bulb of approximately 6500K.
As a light energy penetrates deeper through water, these "red spikes" need to move slightly "left" (lower) on the nanometer graph so as to allow for proper use of PAR (in other words Photosynthetically useful radiation; please see the PUR section). This means higher kelvin lamps of 9,000k to as high as 20,000k may need to be employed.
This can vary with bulb type though as not all so-called daylight bulbs are the same, see the Useful Light Energy section of this article.

*Besides the obvious depth penetration, it is also noteworthy that most green algae need more of the actinic spike than "higher plants", hence the popularity of actinic lights for reef aquariums, however the optimum nanometer range is about 465-485nm, not the lower 420nm many actinic lights produce or the more broad range many "blue" aquarium lights produce of 400-520 nm (this is where the latest technology LED lights "shine", having a more precise 465-485nm blue). For this reason it is a good idea to have extra actinic for corals/clams that depend upon zooanthellic algae, while at the same time limiting blue/actinic in freshwater aquariums to avoid excessive green algae growth.

*Planted Freshwater Aquariums: It is also important to note that freshwater algae also prefer more of the "blue" UVA light so the use of actinic blue lighting should be avoided in planted freshwater aquariums, as well the use of higher Kelvin Daylight (14,000K or especially 20,000K) should also be avoided in all but the deepest tanks since higher Kelvin Daylight lamps produce higher amounts of "blue" light. Otherwise many freshwater plants may not be able to "out compete" against some algae such as hair algae.

*More recent studies show that excessive low UVA (under 420nm) and especially UVB radiation can actually bleach coral, so use of excessive blue lighting under 420nm should be avoided.



Measuring PAR
Although Kelvins (as well as LUX conversions using questionable LUX to PAR conversion factors) are ways of getting rough estimates of PAR, only a Specific PAR Meter (also called Quantum Light Meters) can give you the best measurement of this aspect of determining your tanks lighting requirements (both at the surface and under the surface)
(Here is a link to a PAR Meter Apogee MQ-200 PAR Meter)

Currently accepted numbers measured as µMol•m˛•sec (also referred to as micro mols or mmol) are 50 mmol for most plants or low light corals such as Nemezophyllia, while Acropora can require PAR outputs as high as 300 mmol (any higher is simply a waste of energy/light)

HOWEVER, keep in mind that a PAR Meter is not accurate in important light energy spikes WITHIN the 400 to 700 nanometer range, so while one light might measure a higher PAR mmol reading, another light might be still superior due to the more important PUR output (this is where I have found the use of a PAR Meter over rated by some).

Some organisms, such as Cyanobacteria, purple bacteria and Heliobacteria, can make use of the unusable light discarded by the plant kingdom, in this case, light outside the PAR range required by plants, which is why Cyanobacteria thrive in lighting conditions that include the more yellow 4000 K and below and why actinic (50,000K) as well as balanced light in the 6400 to 14,000K range combined with passing water through an ultra violet sterilizer (to kill free floating Cyanobacteria) is important for control.

In the case of Red Slime Cyanobacteria, these Cyanobacteria do not use the PAR spikes at 465nm and 675nm and instead utilize more of the middle yellow and green light spectrum that is most common fluorescent (even so-called aquarium fluorescent lights) and incandescent lighting.

*Please do not confuse the term PAR (Photosynthetically Active Radiation) used in plant growth as discussed here with another use of the same term in lighting which is Parabolic Aluminized Reflector. This type of light is used for stage lighting and should not be purchased for marine, freshwater, or Greenhouse use under the mistaken belief that these lights are "great" for plant/coral growth.


*For further reading (references) about PAR:
*Light and Plants
*A rational approach to light measurements in plant ecology
*Photosynthetically Active Radiation
*http://www.aquariumpros.com/articles%20PDF/lamptypes.pdf


*Fish Health:
Many recent studies have shown the importance of full spectrum lighting (which will generally encompass a high PAR value) as it relates to health in humans & animals, can be extrapolated to fish as well for a disease prevention which is why good lighting should not be restricted to Reef Marine or Planted Freshwater Aquariums, but to fish only salt or freshwater tanks as well.
In fact the medical community is now utilizing 6400K SHO lights (& similar full spectrum lights) due to increasing studies that show better immune function, mental health, and more. Animal studies support similar results as well.


See these references:
*New Science Sheds Light on Immune Deficiencies
*Light as a NutrientBack To Top


5: Useful Light Energy (PUR):

Useful Light Energy, Daylight CFL and LEDPUR (Photosynthetically Usable Radiation) also known as "Useful Light Energy" is what concerns us as aquarium keepers even considerably more than PAR in providing correct lighting (yet provides a lot of confusion, especially when considering LED Lights).
PUR is that fraction of PAR that is absorbed by zooxanthellae photopigments thereby stimulating photosynthesis. As noted above, PUR are those wavelengths falling between 400-550nm and 620-740nm.
Generally a Spectrograph is used to rate PUR (these are much more expensive than a PAR meter, with the result of many falsely considering PAR and ignoring the more important PUR.)

It is noteworthy that whereas higher plants (generally kept in planted freshwater aquariums) require more of the infrared aspect of the PAR Spectrum while the zooxanthellae found inside many sensitive corals require more of the Blue spike 400 -550 (465-485 in particular according to more recent research). For this reason either/both higher Kelvin Daylight and actinic/blue is required for many reef aquariums.
*As noted in the PAR section the exact nanometer spikes will need to be lower so as to provide the actual PUR, for this reason popular a "red" 5000-5500k plant light is NOT the best light for any water application except for very shallow water since the spikes are not adjusted for water penetration. Balancing these plant lights such as the "Aqua Flora" with 6500k to 10,000k lights is necessary for best results (such a combination may have the added benefit of certain plants growing more toward the surface).
*It is also noteworthy as per recent head to head studies with acopora corals that photosynthetic corals found in waters increasing in depth have adapted to PUR of increasingly bluer light spectrums and thus lights with too much red can actually stop coral growth altogether.

The ability of newer technology lights to pin point the exact nanometer spectrums in output results in much less wasted energy and allows for a light of considerably lower wattage to actually out produce another bulb of higher wattage that wastes much of its energy in light bands that are not useful for life processes (this is major reason the "watts per gallon rule" is so useless when applied to modern technology, yet it is still thrown around by many).

Even the best of fluorescent lights that are a Kelvin temperature of 6500 K use a percentage of their light energy in the yellow and green light spectrum which is mostly useless for aquarium plants or corals (LEDs & modern T2s/ T5s do not suffer as much from this problem from what I have observed using a light filtering lens).
This is where although a 6000-8000K light generally will provide good PAR often there is also more yellow/green light. When used in water applications (especially as depths increase), one aspect of a higher Kelvin (10,000- 14000K) daylight lamp is more efficient penetration (although Kelvin temperatures much over 14000K loose much of the important 700nm "spike" & should be avoided as the only light source)

The picture above demonstrates this with two 15 Watt CFL (30 watts total) vs. one 12 Watt Marine White LED (all white 14,000K emitters). This picture is taken with a camera that filters out certain wave lengths allowing for a better viewing of the difference which is otherwise not easy to discern, however the picture shows how the LED on the left has less of this wasted yellow and green than the CFL lights on the right.
Otherwise the light output appears the same, although this is still important when you consider that this is achieved with only 12 watts of LED vs. 30 watts of Compact Fluorescent lights.
Please click on the pictures to enlarge

Light Spectrum between Reef White LED and 5000 K CFLWith some LED Lights, new technology LED emitters can be selected for the exact wavelength of light, thus much less useless yellow or green light is emitted, so although the LED may seem less bright than some HO lights with the naked eye (such as T5s or MH) the actual output of light energy in spectrums we cannot see is much higher. This is why gauging a light by what you see is highly inaccurate.

The Picture to the left shows the light spectrum as seen through a special 3D lens which breaks apart the light spectrum. This provides a dramatic example of how much of the light energy the 4000K CFL is in the useless yellow spectrum (the 4000K is not a terrible bulb either, as many still use this for plants). The TMC Reef White shows a much more complete light spectrum and much less wasted energy in the useless light spectrums.


IMPORTANT Further/Newer Information as to Useful Light Energy:

As alluded to earlier in this section, EVEN a Spectrograph (which I admittedly use to make certain points) should not be the only determining factor for "Useful Light Energy" as these only rate the light spectrums of a light in air, NOT under water so as to determine PUR. However when increasing depth of water are thrown into the equation (in particular for photosynthetic marine life), these spectrographs become less accurate as these corals and other photosynthetic marine life have adapted to the wave lengths of light energy that reaches their depths, which the spectrograph cannot show.
Obviously this is more blues and/or "bluer" daylights (such as 14,000k or 20,000k).
For this reason I prefer the less scientific, but in my opinion more accurate term of "Useful Light Energy" over PUR.
This also has implications even in equal quality but different lights such as a TMC Reef White 1000 (with 14,000k daylight emitters) versus a TMC 1500 XG. The 9000k emitters in the 9000k XG are simply not a good light energy source for tanks over 24 inches, but are an excellent source for tanks under 20 inches (especially under 15 inches).

Further explanations to hopefully convey the importance of the concept of "Useful Light Energy";

*I have noted that a dozen "hardware store" cool white fluorescent lights can provide adequate lighting for a planted aquarium and even basic reefs, however it would only take a few correct kelvin (for the application) T5 lights to accomplish this same task. The point is that even a T12 cool white provides some useful light energy, but it takes copious amounts of these lights (& wattage) to work correctly (in other word many more watts, which again speaks against the "watts per Gallon rule")

*In another comparison, one can use one of the many cheap LED panels commonly sold that use 90-120 watts or more to light a reef or planted aquarium, or you can use a LED Fixture that utilizes the best technology emitters available such as only found in many TMC AquaRay LED Lights. This is similar to the above example as lower end emitters do not pin point the important light wave lengths the best patented emitters can (think about lighting your aquarium with 100's of LED flashlights, would you do this?).

*As a final comparison, it is important to note as per PUR, that for instance one 6500k light is not the same as another as there is more than one way to mix light "colors" (wave lengths) to achieve a certain kelvin temperature rating. Think about how mixing all paint colors will produce black, while the mixing of all light energy produces white. We as humans may notice this to some degree, however we do not have the ability to pick out particular colors such as a honey bee can; as well photosynthetic aquatic life also has differing abilities to pick out the useful light energy it needs for life processes and even though the kelvin temperature may be equal, the light energy that provides this kelvin "color" is not.

The point of these comparisons is you simply cannot compare apples to oranges when it comes a high wattage of T12 cool white lamps versus targeted T5 (or T2) as well as the "cheapie" LED panels with high wattage versus high end LED such as the AquaRay.
In fact even with the "high end" LEDs by TMC, the Reef White 1000 Ultra produces a higher PAR than the TMC 1500 XG Ultima, yet the 1500 XG (9000k) produces more PUR at depths 12 inches or less!

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6: LUMENS:

The international unit of luminous flux or quantity of light used as a measure of the total amount of visible light emitted. The higher the lumens, the "brighter" or more "intense" the light looks to the human eye. You can figure lumens per watt by dividing the lumens your lamp lists by the wattage the fixture lists.

Knowing your lumens per watt is often as or more important than watts per gallon. For example a T12 light that is rated at 20 watts with a total lumen output of 800 lumens has a lumen per watt output of 40. While a 13 watt T2 bulb rated at 950 lumens has a lumen output of 73 lumens per watt. This is a clear example that the watts per gallon rule is severely flawed as the 13 watt T2 (or two of these) is clearly the better choice for a 15 gallon planted aquarium (or reef) and this does not even take into consideration the PAR rating which is also important for plants/corals or lumens per length of bulb (space). This lumen comparison also applies to SHO, VHO, and Metal Halide all of which far out produce most T12 lamps in lumens per watt.

Focused Lumens;
It is also noteworthy that even the lumen output can be deceiving when considering aquarium lights; LED are a good example of this as these newer technology lights have extremely focused light energy with little essential light energy lost (such as by Restrike), unlike almost every other type of aquarium light currently available. With this focused energy a LED often requires half the lumens (or often even less) to provide essential light energy (such as PAR) to plants, corals, etc. The newer generation LED lights have considerable less loss of lumens at 20 inches than a CFL light (as per tests that show 166% more lumens for the same wattage LED as compared to a common CFL of equal wattage). As another example, think lasers, although not nearly as focused as a laser, modern LED emitters (such as the Aqua Ray) are much more focused than other types of commonly used aquarium lights.

Caution as to using Lumens as a useful measurement of Light Output:
While lumens are a important useful measurement for standard household light bulb comparison, it is only a part of the equation for aquarium use, especially when this measurement is applied to new technology lights employed by aquarium keepers (such as LEDs).
As an example of just one aspect where the lumen measurement falls short is when Kelvin is considered; a bulb emitting 1000 lumens at a color temperature of 20,000K will not emit as much PAR as a bulb emitting 1000 lumens at 6500K.
More over, when compared to "Useful Light Energy" (PUR), Lumen output falls well short as useful comparison of light output. This said, I am not saying Lumen output and focused lumens are useless, as these parameters are a piece of the light parameter "pie", but often it is overrated and these parameters should only be taken as a part and a small part at that when compared to PAR and especially PUR.

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7: WATTS:

Watts equal one joule of energy per second. For us, it's a measurement of how much energy our light fixture is using NOT of light output! This why the 3-4 watts per gallon for FW plants (3-5) for reef can be deceiving, and this rule is only a starting point similar to the 1 inch of fish per gallon "rule". This archaic rule was more accurate when all that was used were T12 lamps which is what this rules is based on.
Keeping this in mind the average T12 has a lumens per watt rating of 40, which means you would need half as many watts of a bulb that produces 80 lumens per watt (assuming PAR, Kelvin and other aspects are equal)

The term "watts per gallon" is getting more archaic as newer T-2, T-5, compact Fluorescents, the SHO, and especially the new reef compatible LED lights. Keeping this in mind; 'watts', when applied to a standard fluorescent tube are spread over longer bulbs as the wattage increases. For instance a standard 30 watt T 8 bulb is 36" while a standard 20 watt T-8 bulb is 24". For high light requirements such as plants or reefs, at least 1 inch per watt is required when comparing tube style fluorescent bulbs.
Many high output light such as the Metal Halide or the more economical SHO PC bulbs use a lot of 'watts' in a small amount of space. The 110 watt SHO bulb uses 110 watts in 10" or even less if mounted in a pendant.

Another aspect of watts is the output of lumens per watts actually used. As a comparison when lumens are considered; the actual output of a 400 watt incandescent bulb is about 25 watts of light, a 400 watt metal halide bulb emits about 140 watts of light. If PAR is considered to correspond more or less to the visible region, then a 400 watt metal halide lamp provides about 140 watts of PAR. A 400 watt HPS lamps has less PAR, typically 120 to 128 watts, but because the light is yellow it is rated at higher lumens (for the human eye).
Wattage of lights versus PUR is where the actual watts used when comparing one light to another is simply not at all accurate, such as comparing a MH or LED of say 75 watts to T12 cool white Fluorescents also of 75 watts; these cool white T12s will simply not even be close to "useful light energy" output at 75 watts as the LEDs or MH (of coarse other factors apply to the MH and LED as not all are equal here as well).

The bottom line is 'watts per gallon' can be used when comparisons are "apples to apples" such as one Patented High output LED emitter to another, but not when comparing a T8, to a T5 to a T2 , to a Metal Halide and especially to an LED.
An example of an "apples to apples" comparison would be the Patented emitters used by TMC require .8 watt per gallon (or less) under 24 inches of water for high light requiring reef life (.6 watt per gallon or less for planted freshwater aquariums).

8: CRI:

To help indicate how colors will appear under different light sources, a system was devised some years ago that mathematically compares how a light source shifts the location of eight specified pastel colors on a version of the C.I.E. color space as compared to the same colors lighted by a reference source of the same Color Temperature. If there is no change in appearance, the source in question is given a CRI of 100 by definition. From 2000K to 5000K, the reference source is the Black Body Radiator and above 5000K, it is an agreed upon form of daylight.

A CRI of 100 has a heavy red spectrum. The color temperature is 2700 K for incandescent light and 3000 K for halogen light. An incandescent lamp, virtually by definition, has a Color Rendering Index (CRI) close to 100. This does not mean that an incandescent lamp is a perfect color rendering light source. It is not. It is very weak in blue, as anyone who has tried to sort out navy blues, royal blues and black under low levels of incandescent lighting. On the other hand, outdoor north sky daylight at 7500K is weak in red, so it isn't a "perfect" color rendering source either. Yet, it also has a CRI of 100 by definition.

CRI is useful in specifying color if it is used within its limitations. Originally, CRI was developed to compare continuous spectrum sources whose CRI's were above 90 because below 90 it is possible to have two sources with the same CRI, but which render color very differently. At the same time, the colors lighted by sources whose CRI's differ by 5 points or more may look the same. Colors viewed under sources with line spectra such as mercury, GE Multi-Vapor® metal halide or Lucalox® high pressure sodium lamps, may actually look better than their CRI would indicate. However, some exotic fluorescent lamp colors may have very high CRI's, while substantially distorting some particular object color.

Technically, CRI's can only be compared for sources that have the same Color Temperatures. However, as a general rule "The Higher The Better"; light sources with high (80-100) CRI's tend to make people and things look better than light sources with lower CRI's.
Why use CRI if it has so many drawbacks? It's the only internationally agreed upon color rendering system that provides some guidance. It will be used until the scientific community can develop a better system to describe what we really see. It is an indicator of the relative color rendering ability of a source and should only be used as such (Source: Color Rendering)

To be blunt, CRI is NOT a parameter that is important in determining the best aquarium light, but it is included here since many mistakenly tend to consider it an important parameter, in fact most lights sold with CRI ratings prominently displayed are intended for home or industrial use, NOT aquariums!
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AQUARIUM BULB TYPE:

Aquarium Light Types Explained Here Include:
• T8 & T12, • T5, • T2
• VHO, • CFL, • SHO
• Metal Halide, • LED, •Lunar
• Induction, • HID Xenon


  1. *T-12;

    2. A standard pin, 1-1/2" wide bulb. The main caution to the use of these bulbs for aquariums, even though many forums often suggest this, is the use of shop lights as an inexpensive alternative to many aquarium lights. A 4100 K cool white shop light is not going to come close to a 6400 K daylight lamp that is of peak PAR efficiency (even if you match lumens). This bulb will generally use more watts and have a lower lumens per watt ratio (usually around 40) and is common in shop lights and even many aquarium bulbs. These are generally the least expensive lamps to purchase and even though they may be "old school", some still try to make up for the low technology with the fact you can purchase several for a low price to make up for poor efficiency.

    *T-8; A standard pin, 1" wide bulb. As compared to the T-12, a 48" T-12 will use 40 watts, while a 48" T-8 will often use 32 watts (although not always). Even though the watts are higher on the T-12 the T-8 is more efficient with less wattage. The T-8 is the more common bulb/lamp size in many basic aquarium lights.


  2. *T-5;

    3. Generally around 13 mm in diameter. This is a mini pin bulb which generally uses even less watts per lumen than many than T-8 bulbs. A common lumens per watt output for T-5 lamps is around 65.
    The T5 has become very popular among both plant keeping freshwater aquarists and reef keepers for good reasons; they are compact, come in many varieties and high lumen per watt outputs (as a broad generalization only requiring 2 to 4 watts per gallon for more shallow planted/reef applications depending upon tank depth and other factors). As with T2 Lights, T5 are generally not well suited for deeper tanks over 20 inches

    • One negative with T5s is that the quality control on these lighting fixtures (not the bulbs themselves) is often lacking. This problem tends to be with some of the HO (or VHO) T5 light ballasts/fixtures, and in fact tends to be a problem with VHO Compact Light Fixtures as well. For this reason my recommendation is to avoid the VHO or HO T5 or Power Compact CFLs and stick with the standard output versions. If higher output is needed consider the newer technology SHO, LED or MH lights instead, in fact when cost per lumen as per lifespan is considered, a LED Aquarium Light Fixture is now a much better deal (since LEDs last 50,000 hours vs. the common 8000 lifespan of a HO T5 or VHO Power Compact).

    Another consideration for higher output requirements, such as large planted freshwater aquariums, consider the vastly superior in terms of performance and cost SHO light over the T5 (the T5 is a good light, but it is often pushed by aquarium keepers that are not aware that technology has passed them by).

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  3. *T-2;

    4. T2 Aquarium Fixtures, LightsThese bulbs are the latest fluorescent technology yet (LED are advancing even more). They measure only 7 mm and allow for several bulbs in a small space. A 13 watt 20 inch T-2 Bulb (6400 K) produces 950 lumens which is 73 lumens per watt in a very small space with low wasted green/yellow light energy that is often found in other Power Compact Lights! As little as 1 to 1.50 watts per gallon for a planted aquarium is all that is needed from these T2 Lights! (depending upon tank depth, and not for tanks over 20 inches max; consider SHO for tanks over 18 inches).

    Quite bluntly, these T2 lamps and fixtures are about the best bulbs in a small space I have seen! These are very useful for small to medium planted aquariums or Nano Reefs or even shelves for betta breeders (although ONLY as a compliment in larger aquariums over 20 inches in depth for freshwater and 16 inches for marine).

    The linkable fixture feature (although some T5s also have this neat feature) is also a nice aspect of these T2 lights/fixtures (this allows for use in larger aquaria such as 60 gallons PLUS). Some T2s can be linked with small extensions (that are available with these T2 fixtures), these allow you the choice of either placing a T2 in series (end to end) or in parallel (which is useful if you desire a higher output yet in a small space or to utilize a daylight and blue/actinic light parallel to each other) with out having to add multiple outlets/plugs.



    The newest generation T2 Lights require less watts to provide the same useful light energy (in particular required by plants & coral) than all other lights except for LED.
    Speaking of LED Lights, the T2 makes an excellent compliment to LED Lights (for cost savings as well). The picture to the left displays a newly set up planted freshwater tank that has 4 GroBeam 500 LED and 4 6400K T2s as well as a Mylar Reflector (there are many locations selling Mylar including online).

    (Please Click the picture to enlarge)

    When all important parameters are considered (PAR, useful energy, lumens per watt, etc.) the a typical 6400K T2 about 40% of the wattage of a standard T8/T12 aquarium light for the same useful output (a 13 watt T2 will equal 30 watts of most older fluorescent aquarium lights). The T2 will even exceed a comparable T5 light by about 20% in useful light energy output in up to 20 inches of water.



    I expect these new T-2 lamps to sweep the small to medium aquarium keeping hobby (especially planted FW and Nano reef) due to their extremely high efficiency and out put. (only LED lights are more efficient, please click on the picture to the left for a comparison).


    In fact these lamps are even a good choice for many aquariums such as 60 gallons and larger since each fixture can be linked together forming a larger fixture (similar to some T5 fixtures, which are also good fixtures, just not quite up to the more modern T2 in efficiency vs. output). For instance I have used two T2s linked together for some 60 gallon FW aquarium and two sets of two (placed in parallel in the hood) for planted 60 gallon FW aquariums.
    T2 Fixtures/lights also work well in Marine Aquariums (particularly pico/nano reef) since these lamps in the 6400 K version have a high output in PAR required for symbiotic algae that live within corals. As well actinic/blue versions of the T2 light are now available to the consumer.

    One negative with the first generation T2 as compared to the older T5 is that there are not the selection/variety, however as noted in the previous paragraph, blue/actinic T2 lights are now available to the hobby.
    As well, there is not as much need for some of the versatility other lights, as the T2 has its own versatility such as small space combined with higher lumen per watt output.

    I would also counter uninformed aquatic forum comments such as this one: "T2 are still pretty much a niche market that could be easily overwhelmed by the T5 and they could disappear at any time or just become even more expensive". The answer is both yes and no. The T5 at one time was still a niche market as well, and more importantly the T2 has grown considerably popularity in Asia (possible due to space concerns) and even in small scale Hydroponics/home green house applications in North America. Statements like that are why the aquarium industry is often a decade behind other industries in adapting new technologies (if at all in some sad occasions).

    One other negative with first generation T2s that goes for T5s (especially the expensive HO version of T5) is that the quality control on these lighting fixtures (not the bulbs themselves) is often lacking. From my investigation of looking at defective items, it seems to be difficulties in good solder in the confined spaces of these small micro lighting fixtures. This problem seems to be a first generation problem of T2, as the newer (second generation) T2s we are now using do not seem to have this problem with early tests. As well the problem of short ballast lifespan does not exist as it does with the VHO version of T5 lights, but then a VHO version of the T2 does not exist.

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  4. *VHO Power Compact

    5. Via Aqua new generation Helios VHO fixtures, lamps This stands for "Very High Output". These come in T-5 thru T-12 standard fluorescent tubes and in the newer power compact (usually 4 pin) lamps such as the popular Current USA, Coralife Quad & New generation Via Aqua Helios VHO .

    The new Helios & other VHO Power Compact Fixtures come in a variety of sizes with outputs up to 180 watts out of lamps under 40 inches in length, which rival many Metal Halide (although not in depth penetration). These new higher output VHO fixtures/lamps have higher Kelvin and wattage output than previous generation VHO lamps/fixtures of similar size. These can be used for both marine reef applications as well as freshwater planted aquariums (these new VHOs are not scheduled for full release to the public until early 2009).

    Coralife Quad VHO light Coralife has a new quad lamp VHO (such as the 20 inch; 96 watt fixture) that have high output in small space.

    However both these before mentioned lighting systems are a bit pricey in my opinion for the "light out" for the price paid. As well the electronic ballasts contained in not just these, but ALL these VHO styles of CFL light fixtures (Current USA, JBJ, etc.) tend to have a short life span of under 3-5 years in my experience. When the ballasts go out, generally the replacement cost is the same as a new fixture.

    With this in mind, I would recommend the SHO Lights which only require an inexpensive incandescent fixture and are vastly less expensive the similar high output PAR light (for example: $35.99 for a 105 watt SHO). I should also note that as of my latest update of this section (VHO), I have found their durability in relation to cost, and output in essential lighting parameters (not just the way out of date watts per gallon so called rule) is not as good as the up and coming SHO or especially LED Lights, which in my tests, feedback, research and experience are the future of aquarium lighting, especially as it pertains to freshwater plant and reef aquariums.

    More bluntly, I would generally advice aquarium keepers to avoid the often over hyped VHO Power Compacts or HO T5 in lieu of the SHO, LED, or Metal Halide for high end lighting needs or stick standard CFL or T2 Aquarium Lights for cost effective aquatic lighting needs.

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  5. *PC (or CFL);

    6. Compact Fluorescent light bulbs, standard screw in baseThis stands for "Power Compact" or "Compact Fluorescent Lamp (light)". These bulbs come in straight pin arrangements, square pin arrangements, and the self ballasted standard incandescent fixture "screw in" type. These bulbs are similar to T-5s and have about the same lumen per watt output (generally around 60 lumens per watt).

    The standard medium base version of these lamps will fit in a common incandescent light fixture, making these lights about the most economical lights you can purchase with this kind of output. These are an excellent choice for use in planted Freshwater or even Marine.

    Aquarium Incandescent fixture with 6400 K Compact fluorescent lights These can be used in a basic Nano Reef tank under 30 gallons, especially when the hood already contains incandescent fixtures, as you need not purchase special fixtures for these.

    See the picture to the left as an example, please click to enlarge

    These self ballasted high PAR lamps are inexpensive and make it easy for even an aquarist on a budget (even a freshwater fish only tank) to provide the best possible lighting within a budget for fish, plant, and even basic Nano reef health!

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  6. *SHO Power Compact Lights:

    7. A newer Power Compact that in my opinion is awesome for planted aquariums (in fact the best other than some high end LEDs for planted freshwater aquariums). As well the SHO can be used for reef aquariums (as an addition to LED or Metal Halide)
    The SHO Light is currently sold in a self ballasted PC bulbs/light. The 105 Watt SHO Daylight bulb puts out 6300 lumens and is comparable to a 525 watt Standard bulb (click on the picture for a link). This comes out to 60 lumens per watt; however this is a deceptive guide, as you can fit many more of these bulbs in a given space and also utilize more efficient reflectors.



    SHO Light, 6400 K Daylight LitThe SHO is already VERY popular with Green Houses/hydroponics and is growing in aquarium use popularity, although it is still relatively unknown to many in the aquarium hobby (although many forward thinking planted FW and some reef keepers are aware of these lights now).
    In fact the 105 Watt SHOs were in short supply during the spring of 2009 due to just one company purchasing 1000 of these for lighting greenhouses.

    My point is; if a company (greenhouse business) that needs the correct lighting that are price effective to grow plants for a business, all the more reason these should be used in many freshwater plant aquarium applications (& even many reef tanks as well due to high PAR and output needed by zooxanthellae living within corals, complimented by actinic LEDs or MHs).

    Keep in mind that there is vastly more research $$$ into horticulture than into aquarium keeping (the money generated by the aquarium industry is just a needle in the haystack compared to most other industries), sadly this point is missed while many continue to use older less efficient, yet often more expensive lighting technology for their planted aquariums.

    In fact the medical community is now utilizing these SHO bulbs (& similar full spectrum lights, which is also often making the SHO in short supply) due to increasing studies that show better immune function, mental health, and more. Similar animal studies show like results. I learned of this when inquiring as to why the SHO lights were currently unavailable from the North American distributor, and they pointed out that several hospitals and convalescent homes had purchased over 1500 of these lights. They pointed out the simplicity of these Super High Output bulbs are quickly making these a favorite of the medical community for their full spectrum light needs (I now use a few 65 Watt 6400K SHOs in my home after learning this and there is certainly a difference).

    See these references:
    *New Science Sheds Light on Immune Deficiencies
    *Light as a Nutrient

    While there are few drawbacks to the SHO light for aquarium use; one such drawback is that in any "tube light" some of the light that shines up from each tube just reflects right back into the tube and is lost (this is called "Restrike"). HOWEVER, the spiral design & especially the use of a reflector tends to limit this minor problem and based on extreme plant growth achieved this is obviously not as much a factor as some may claim (this is essentially a problem with ALL compact Fluorescent lights).
    As well, while the SHO does not produce nearly as much heat as a Metal Halide, the simple fact of the wattage used by these lights still produces heat, so a well vented hood or the use of a reflector is advised (any light should be placed in a ventilated hood/canopy as trapped moisture can quickly damage any light whether an SHO, T5 or LED).
    Finally the only other potential negative is that these SHO lights are more of a DIY lighting application, not an out of the box and place on your aquarium light applications; so those who do not have DIY abilities, time, or simply desire an out of the box light might find this is not the light for them.

    Back to the positives of Super High Output lights; quite bluntly there are few equals for high output aquarium lighting (especially for planted freshwater aquariums), especially when cost is considered (as well as other positives) since these lamps do not require expensive ballasts like a MH (SHO are self ballasted) and generally cost $30 and up per lamp.
    Since the 6400K SHO requires as little as 2 to 2.5 watts per gallon for the most light demanding plants; Four 85 watt SHOs (or 105 watt for even higher output) can easily handle a 6 foot FW 125 gallon planted aquarium (some T2 or T5 can fill in some more dim spots if necessary)
    While in Marine Reef Aquariums this same combination (maybe using 105 watt SHOs) along with one or two LED Lights (such as TMC Marine Blue) would work in most reef applications for $500 to $800 for a large aquarium (less for smaller aquariums, or in combination with LED). Consider the 65 Watt SHO for smaller tanks of depths under 15 inches.

    SHO lights in twin socket with reflector diagramThe SHO can be mounted into your hood using a standard incandescent fixture. I recommend using an aluminum foil or better an easily made mylar reflector to amplify light downward (& reflect heat away from the canopy). I also recommend venting the hood to remove heat and moisture (a small outward direction fan can be helpful too)

    The SHO light is most effective hung as a pendant light using reflector similar to how Metal Halides are commonly installed over an open aquarium. These SHO lamps are also an excellent compliment to MH, VHO or other "strip" lamps for use in reef tanks (in part due to their high intensity in small space and PAR output which is important for the symbiotic coral/algae relationship). Research (albeit older research now) has shown that many stony corals, clams, and other sessile species that depend on photosynthesis of zooanthellic algae not only thrive but also propagate when maintained under Power Compact lighting alone, and the SHO power compact has a MUCH higher useful light output over standard CFL.

    SHO over planted freshwater aquarium The picture to the left shows one way of DIY mounting of a SHO light with a reflector by designing your own "rail" system that fits on the aquarium top. Multiple SHO Lights can be added with just such a mounting system
    This tank shows just one of many simple ways to install a SHO light which also includes hanging pendent style, or inside of a canopy, but this picture shows my favorite method.

    Please click the picture to enlarge

    As of the most recent update of this section of the article, the SHO is easily one of the lights of the immediate future for aquarium lighting (the others are the quickly improving LED aquatic light & T2 and some of the newer T5), in particular planted freshwater aquariums or some reef aquariums. This is not to say that MH or VHO are bad, it is just when you consider all the aspects of aquarium lighting parameters (not just the out of date watts per gallon rule), then throw in costs of purchase, reliability (a problem with many VHO & some T5 lights) lower heat output (the main issue with MH); there is simply little comparison at this time.

    In summary as to SHO lights for aquarium use, what I find amusing is that the only negative comment I have had from someone who actually used an SHO in his 30 Hexagon is that his plants grew TOO FAST with constant pearling and he could not keep up with them due to his work schedule. Honestly this negative is positive proof of these lamps abilities!

    In fact, even with quickly improving LEDs (see later in this article), the SHO may still be your best choice when price is considered (it is still often the most popular choice for Hydroponics or Planted Aquariums).

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  7. *Metal Halide (MH);

    8. metal halide, MH aquarium light, 20K Metal Halide was generally considered the "Kings" of reef aquarium lighting due to depth penetration, output, spectrum, and over all beauty and amount of coral life they help support making most corals "pop" with life (however the newest HO LEDs are now over taking the MH and the keyword is "was"). Aesthetically speaking the Metal Halide is also hard to beat, however the latest technology LED lights are now beginning to surpass MH for Reefs and LEDs have been proven to surpass MH with plant growth in nursery/hydroponics environments (one study/test shows a 12 Watt Full spectrum LED producing better growth than a 175 Watt MH of the same type!).

    That said for tanks over 30 inches in specimen placement, the Metal Halide is still generally the best available light, especially when used in light combinations that include 20,000K, with other popular Metal Halide Kelvin Color Temperatures being 10,000K, and 14,000K (the 10,000K generally providing the best PUR for tanks under 20 inches in depth).

    As for other light comparisons to the MH, even the newer T-5 lamps cannot achieve the depth penetration and overall output of these lights. Metal Halides generally have very good lumens per watt ratio (although I have seen a lot of variation and even incorrect ratings here); however it is safe to say that MH are generally found with lumens to watt ratios of 50 to as high as 90 which is among the highest of any aquarium lights available (along with excellent PAR production as well).

    Metal Halide work via a gas mixture of halides and other elements, the actual light production comes from the small bubble of gas that is held in place by metal wires and/or supports. The electricity running between them and the small gas bubble, heats them, similar to an incandescent filament. This is one of the reasons that Metal Halide bulbs give off more heat than other bulbs.

    MH Lights are generally sold in two basic types for aquarium use: the Mogul base & the HQI Double Ended Metal Halide bulbs.
    Mogul base screw in Metal Halide bulbs for Aquarium use come in a variety of color spectrum from 10K to 20K (the bluest)and wattages from 250W - 1000W. German made (Ushio) metal halides have an excellent reputation for producing the best lighting effects for reef aquariums.

    The newer Halogen Quartz Iodide (HQI) lighting systems are used mostly on saltwater reef aquariums. HQI bulbs are commonly offered with spectrums of 10,000K and 20,000K. These high-intensity bulbs help corals thrive, but give off less heat than regular metal halide bulbs. HQI Double Ended Metal Halide bulbs have been used in Europe for many years have gained popularity in the U.S. among aquarium hobbyists in the last several years. Double Ended MH HQI bulbs offer many of the same features as standard mogul base Metal Halide bulbs but are designed differently. These bulbs are much smaller than mogul base screw in Metal Halides and are double ended. The benefits of using HQI Metal Halide bulbs are that they offer a more clean color spectrum (useful light energy/responsive wavelength), are more efficient, produce slightly less heat, and last longer than standard Mogul Base metal halide lamps.

    Eco Systems Metal Halide lamp and fixture The downside is the heat that MH lights produce, often resulting in the need for hood fans and even chillers, although the newer open design units such as the EcoSystems USHIO double end fixture and HQI bulb works well for 10-25 (or even larger aquariums when other lights are included in the "mix") without a chiller.

    The sizes I most often have used are between 10,000K and the 14,000K with 75 watts for small aquariums up to 400 watts for really deep tanks (over 30"). With the 10,000K- 14,000K lamp what I currently recommend.

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  8. *LED (light-emitting diode):

    9. Quickly becoming the new king of aquarium lighting (at least with the new "high end" HO/PUR LED emitter bins), with the same shimmering effect and "popping" of coral life otherwise found in Metal Halide. This aquarium light type uses semiconductor technology as its light source. The difficulty in the past (and where many still misunderstand the complexities of LEDs) is correct wave length of the emitters.

    Achieving the correct wavelengths in the correct amounts has been the challenge and why a simple LED flashlight has about as much in common to an advanced aquarium LED as a paper glider to an 747 jet airplane. This however is also the advantage as much of the useless green and yellow light spectrums can be omitted as well.
    Another challenge has been the sophisticated circuitry required to control voltage for delicate high end emitters from spikes or drops in voltage. As well new power supplies (ballasts/drivers) are in development that can add 10% more output from the same LED emitter.

    The new reef compatible & freshwater planted tank LED's are likely to take over the market along with the T2, T5, & SHO lights as the better LED fixtures become more readily available, the price comes down, PUR (useful light energy) & general aquarium compatibility come up. Correct emitter PUR/Kelvin technology has been a barrier in the past and continues to be the problem with the plethora of LED fixtures made in the same factories using the same lower technology under multiple brand names and sold at most aquarium stores.

    In addition these lights do not have the heat problems, often last 50,000 hours, produce less useless yellow/green spectrum light (in aquarium adjusted configurations), and are very compact. In fact this lack of production of yellow/green light in many all 'high end' emitters used by various LED Kelvin lights (whether 6500K or 14000K) often makes the LED look less bright to the human eye, when in fact the opposite is true as per useful light energy.

    High end LED lights that utilize the proper Nanometer output emitter bins may prove to be more suitable for aquatic life tank-lighting and reef tanks because they offer superior flexibility when compared with traditional fluorescent lighting & even Metal Halide. When LED lights operate, the photometric radiation remains within a narrow band on the electromagnetic spectrum. Specific photometric wavelengths are often beneficial to some aquatic plant life and reef tanks. Controlling specific wavelengths becomes possible through a basic network of colored LED lights connected digital LED controllers, circuitry, and drivers.
    It is in this area where development costs are incurred and where many who do not understand the business aspects of these costs will question why one LED manufacture has or can have exclusive patent rights or similar. Basically any 'high end' developer is going to want to recover development costs as quickly as possible and "off the shelf" sales is NOT the way to do this; AND TMC, CRee, OSRAM, Orphek, etc. are no different than any other manufacturers in other businesses.
    As an example; Drug manufacturers are similar in development costs, as while not all research and development results in a "winner", the projects that do "pan out" have to pay off and you are certainly not going to find the latest heart medication in a generic package, YET based on a few questions I have received, some persons think this does not apply to LED emitters and similar?

    Since LEDs emit light only in very specific direction, the installer has the option to illuminate a precise area by simply rotating the polycarbonate tube casing. For this reason the LED does not need to produce as many lumens of light as most conventional lights as many lumens of important light energy is lost due to lack of focus, including all power compacts and fluorescent lights in general, but need higher lumen outputs to achieve the same lighting parameters.

    Controlled Tests with Plants and The Aquatic Life Implications;

    In tests for plant nurseries (Green House, Hydroponics) full spectrum LEDs such as the newer generation TMC GroBeam Aquarium Lights, 3w LED Grow Lights or even the older generation LED Grow Lights have been proven to surpass even Metal Halide Lights in both growth and useful output.

    The picture to the left are the plant growth results comparing the same Kelvin output LED and Metal Halide Lights as measured by a PAR Meter (please click to enlarge view):

    It is noteworthy that the human eye is very sensitive to light in the yellow and green regions (500-600 nm). This graph shows the relative spectral intensity of 2nd generation (not the newest emitters) LED 6500K and a typical HID-MH grow light (6500K), together with the human eye response curve as measured by a PAR meter (for the light output, not the human eye response). This graph also shows why a high performance LED light (of any Kelvin) may not appear as bright to the human eye).

    This controlled test has aquatic implications, as photosynthesis is the same whether it be a terrestrial plant, a freshwater aquatic plant, or symbiotic zooanthellic algae found in corals. The only difference would be that light energy is quickly absorbed by water, especially red light waves and many MH (such as a 14,000K or 20,000) have excellent depth penetration, however modern LED lights such as an AquaRay/AquaBeam 600 Marine Blue have similar penetration.

    It is still easy to make assumptions from the raw data based on this study with plants that a 12 Watt High Output LED (such as the Mini 400 or GroBeam 500 for planted aquariums or the AquaBeam 600 Reef White/Marine Blue for Marine Reef Aquariums) can at least replace a 100 watt MH of equal Kelvin ratings in reef or planted aquarium applications (the TMC AquaBeam Ultra 1000; 30 Watt LED should easily replace one 175 Watt Metal Halide, if not a 250 watt MH of similar rating for marine applications).
    Please click on the picture above/left for a better view of a 40 gallon freshwater aquarium with just ONE GroBeam 500 12 Watt LED as an example of what just 12 watts of high end emitter LED light can do!

    Or click on the video below for a reef aquarium with only three AquaBeam Reef White 500/600 12 watt LED Strips:

    YouTube Video, Red sea max 130 after aquaray mod





    Metal Halide comparison with LED LightsBack to the Controlled Tests with Plants:

    The picture to the left shows the useful PAR light energy of a MH compared to a LED Light (both full spectrum daylight).
    Please note that this is an older generation "Full Spectrum Daylight" LED used in this controlled test, not the newest generation GroBeam or higher Kelvin Marine White 14000K.

    Legend
    *Dark Blue = LED Lights (6500K)
    *Light Blue = Necessary PAR Spectrum of Chlorophyll
    *Lavender = Metal Halide (6500K).

    There are mixed reviews on the older generation larger units such as the Solaris (which is basically the first generation of LED aquarium lights & quite pricey at that) and earlier TMC LEDs as well when compared to MH light fixtures, I personally did not find LEDs practical for Reef or Planted Aquarium Lighting until 2008.
    However the newer 3rd generation and lower cost TMC Aqua Ray are a vast improvement in price/affordability and PUR output; in fact at the price of the AquaRay LED Aquarium Light Strip, coupled with the 50,000 hour lifespan their actual light cost per hour for comparable output is actually favorable to most available aquarium lights.

    More about Emitters:

    Many do not seem to understand that not all emitters are equal even with the open source Cree-XR-E emitters, commonly sold for other applications; these are only as good as their correct wavelength output (Kelvin Temperature/Nanometers). One cannot compare a first generation CREE XR-E or similar emitter from a few years back to the newest XR-E of today anymore than you can compare first generation iPhone to the latest iPhone (same name, improved technology).
    Based on email I get (some very insulting too), forums I have read, & especially YouTube videos (for DIY LED Aquarium Lights) many persons seem to make this very incorrect assumption. This has resulted in a plethora of non reef capable LED lights flooding the market, some claiming to use CRee daylight emitters while in reality these are not even close to the same currently patented emitters used by high end LED lights!
    I do not know whether to laugh or cry when I read or watch YouTube videos where someone brags how cheaply that they put together a DIY LED Fixture, when in reality this is the same as bragging about making your own PC Computer using a circa 2000 Intel processor and attempting to compare it to a computer using the latest Intel processor!

    Since "Blue" light is the easiest to achieve with low end LEDs, this is way to often spot poor quality LEDs (as well as "cool white"), as with common household LED light replacements, these will appear more blue than high end daylight LED emitters.

    Another example are the exclusive Cree Emitter bins used by Tropic Marine Center AquaRay/AquaBeam should not be confused with CRee emitters sold for other lighting applications, as these do not produce the correct Kelvin/Nanometers of Light energy required for delicate marine reef inhabitants and freshwater plants.
    One example is the Daylight CRee XR-E from several generations back that are available to the general public, Chinese manufacturers, and used by manufacturers such as Aqua Illumination, E.Shine, or others and sold under USA brand names (such as Marineland). This older generation emitter ranges from 6000 to 9000K (in the same emitter too!) and has much more of the green/yellow bands and much less of the near infrared bands of light. Another example is the blue emitter bin used by TMC produces a rather exact 465nm - 485nm (which as per our PAR section of this article is the primary UVA wavelength for optimum PAR).
    Worse would be the cheaper no name emitters used by manufacturers such as BaiSheng & others and sold under a plethora of other names for so-called aquarium use; these use daylight emitters that can vary from 2000K to 6500K and are in reality totally useless for aquarium use other than just plain light!

    Think about why a CFL 10,000K daylight is so much different and more expensive than a common household CFL sold in hardware stores, or the many decorative LED aquarium lights or even those for home or flashlight use; try using one of these to grow your delicate coral or plants (the answer is they will not). Sadly shortly before writing this update, I got a obscene email about why should he pay for a Cree emitter in a high end aquarium light such as the Aqua Ray or similar, when he could by these for much less money for other application. This shows the unfortunate lack of understanding of what is important in aquarium lighting, whether LED or other lights (hopefully this is understood better for any reader here up to this point in the article). This is the reason most earlier LED aquarium lights were not adequate for supporting life properly until recently.

    Another misunderstanding about LED emitters is targeting the responsive wavelength, while exact coral responsiveness wavelengths is unknown, much is known in a more broader sense (and even more knowledge is growing such as the "blue band" of coral responsiveness). As an example we do know that much of the yellow and green bands are useless. The unfortunate aspect of this misunderstanding is that these same misunderstandings do not seem to be applied to Metal Halides to which part of their success has been the targeting of responsive wavelengths rather than the "shotgun" approach of lighting in the past.

    It is noteworthy that many other LED lights now on the market such as the Rio Mini Sun, Marineland Double Bright, or "Ecoxotic Stunner" are only for adding highlights and supplemental lighting, not as a primary lighting source. This also is the case for the many submersible LED lights that are also available in stores or the internet (of which the circuitry generally fails due to humidity damage).

    The graph on the left shows the daylight emitter output of the popular Marineland Double Bright 1 Watt 6000K emitter (please click on the picture to enlarge). This graph is very clear that there is none of the essential near infrared spikes required for PAR/PUR, only blue and mostly wasted green/yellow visible light, this is what fools many who measure lights visually as the Double Bright will look bright to the human eye, but in reality is only a highlighting light (observed use in actual reef aquariums has proven this out too)!

    This is similar to the older (now out of date) TMC LED lights from a few years back, however the current TMC LEDs (such as the Marine White) now use the most current CRee emitter bins (with exclusive rights to these patents as noted earlier). The bottom line is the results of top notch emitters such as the patented Cree emitters speak for themselves by professional Reef Aquarium Maintenance companies, Quality Marine and others.

    There is a reason many LED knock offs utilize 100 plus emitters (often 1 watt each although the SkyLED is ONLY .06 watt per low PUR output emitter). These older technology LEDs use a shotgun approach to achieving aquarium lighting (similar in principle to my use of a dozen low end T12 fluorescent light tubes 30 years ago to achieve adequate lighting). A good example of this approach are the Acan Lighting LED lights.
    For those interested in the best in LED technology, the TMC AquaRay as well as the Orphek and a few other truly high end LEDs are your best choices.

    Please note for those who choose to dig up old graphs and diagrams from TMCs website (which is not at all current), I already have provided the most current PAR readings, graphs, etc. and you can either accept or reject this information and the many aquarium keeping professionals that are using or have tested the LEDs I have spoken of.
    Comparing a TMC "Marine White" or "Full Spectrum" (which is not even sold any more) from a few years back to a latest CRee emitter bin "Marine White" is like comparing a cell phone circa 2000 to an iPhone circa 2011!

    Use of LED to prevent Red Slime
    Another positive attribute of LED Aquarium lights as per s recent study (August of 2009) is that LED used in marine aquariums that suffer with Marine Red Slime Algae (Cyanobacteria) can immediately eradicate Red Slime algae when used in a full spectrum lighting configuration. These "immediate" results were just two weeks. I do not know (as of this update) the exact reasons, but my suspicions is that CFL still produce more of the yellow/green nanometer range of light which encourages Cyanobacteria and discourages competing green algae.


    *PAR LED Lights are another newer innovation. These high PAR 6500K LED lights come in many different configurations of varying number of emitters.

    This LED was originally developed for the Hydroponics/ Plant Nursery Industry but has now crossed over for aquarium use. This LED produces very high amounts of useful lumens in the peak PAR with almost no wasted yellow or green light, making this an excellent and more economical choice for planted freshwater aquariums (& even marine aquariums too, especially those under 24 inches). This light is very focused with little spread, making it ideal for intense bright spots, but less than ideal for lighting vast areas of an aquarium. The other unique feature is this light is simple to install via a common household incandescent fixture.
    The picture above/left shows a PAR 38 6500K Daylight over half of a 40 gallon aquarium, demonstrating the high lighting capabilities of this more affordable, yet high output LED.

    *LED Summary; The bottom line is when you compare an LED Aquarium light to the many popular CFLs and even T5s in terms of lumens per watt, focused lumens, PAR/PUR, lower wasted yellow/green light energy, low heat output, energy consumption, long life (50,000 hours vs. 8000 hours), the modern LED is generally a better light even in long term cost since (as an example) a 12 Watt Aqua Ray GroBeam 6500K daylight (either #500 Strip or Mini #400 Tile) can easily replace a up to a 80 Watt power compact (also daylight) when you compare ALL aspects of lighting as presented in this article.
    When compared to even older T8/T12 aquarium lights, a third generation TMC Aqua Ray & Other High End LEDs require only 15% (or less) of the wattage for the required light energy of a planted or reef aquarium (as little as .6 watt per gallon for high light planted aquariums and .8 watt per gallon for Reef).

    The flaws of LED aquarium lights are quickly disappearing and based on the energy savings in electricity in wattage of the lights (as compared to MH) as well as electricity use for air conditioning or the cost of a chiller often necessitated by larger Metal Halides. I should also note that LED light technology is growing by "leaps and bounds" and many of the bugs including price are currently being improved upon.
    In fact for Planted Freshwater the top LED Lights (with the highest PUR) have few limits in their applications.
    While with Reef Aquariums even most of the best LED fixtures still are at their limits at 24-30 inches of water depth for delicate specimen placement

    LED Light systems are easily complimented with T5 Fixtures, T2 fixtures for smaller applications, or even the SHO self ballasted high output CFL for large tank applications (please note that the SHO are currently only available in daylight bulbs).
    See this video for an aquarium with three TMC Reef White LEDs & two CFL lamps:
    Reef Aquarium with Reef White 500/600 LED





    Finally;, I should note to newer readers of this constantly evolving article that may think there is bias toward high end LED lights, you would only be 1/4 correct, as first I do not recommend the plethora of junk LEDs commonly sold and as well if you were to read this same article circa 2007, I did not recommend ANY LED Light, including the TMC AquaRay, however technology had increased considerably in this arena of aquarium lighting.


    Here is a video comparison between 2nd generation LED (circa late 2009) and a more common 72 watt 10,000K light fixture:
    LED Comparison with Fluorescent light

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  9. Lunar (Moonlights)

    10. Often LED as noted above are used as lunar or moonlights. This is an area where anecdotal information seems to be the main information available.

    This includes the common belief that moonlight should be "blue" when in truth all the moon does is reflect diffused sunlight back to the earth (more during full moons, less during other phases). Dust or moisture can affect the color spectrum seen by the human eye as well (which often makes the light appear blue). This means that a dimmed/diffused daylight is a more accurate production of moonlight. This can be done by fading a Reef White AquaBeam LED as an example.

    Essentially these are very popular for marine reef aquariums for both a low level "night light" and for simulating moonlight for corals and coral propagation. Where some of the misinformation comes into play is that many will state that fish need these lights, of which there absolutely no scientific proof and also that corals need these for proper growth which also has no scientific evidence to back this up.
    Aquarium Moon lights (lunar lights) do nothing to aid in this.

    Lunar cycle animation for aquarium What lunar lights (moonlights) could do with correct programming for the marine reef aquarium is to simulate marine lunar cycles which are necessary for some fish and coral reproduction/propagation, as Corals in the Great Barrier reef spawn 3-7 days following the first 2 Full moons in late spring and early summer. Even here there is still a lot of controversy as to what cycle is best and how much light is best.

    From what I personally have observed combined with the opinions of other aquarium professionals is the use of gray nylon filter placed over standard daylights (T2, T5, T8 CFL, etc.) can work as a moonlight; even low level "white" lights such as nightlight bulbs, or even the Rio Mini Sun LED lights can work just fine for this since this has shown to be a more of a low level light issue and timing issue.
    Adding or subtracting the amount/intensity seems to be the secret of simulating these cycles which can be accomplish easily either manually or with electronic timers (that can be set to more accurate monthly 29.5 day lunar cycles of lighting). Strategically placing these lights also shows evidence as to properly simulating this effect.

    Please click on the picture above/left for a larger animated version of the lunar cycle

    If anyone reading this article has good scientific evidence to the contrary (or even to support) what I have just said about the use of lunar lights, please email me on my contact page with these references.

  10. Induction Lighting

    11. Induction Lighting, how it worksAlthough not a new technology per say, it is new in regards to commercial availability as until recently, new developments have broken down the barriers of costs and technological setbacks, such as EMC interference, lumen depreciation, ability to dim and a useful range of available wattages.

    This type of lighting last up to 100,000 hours (often over 20 plus years under normal usage) and is another good candidate to replace Metal Halide Lights. Induction lights do not have the warm up times of MH or similar (20 second warm up vs. 10 minute warm up), use no mercury, have no filaments to burn out, and they produce half the heat (160 F vs. 300 F for a 200 watt Induction Fixture vs. a comparable in output 400 watt MH fixture).

    Induction Lights generally have a high CRI of 82 with a high lumen per watt output (surpassing most MH).

    Currently the main negative as per Aquarium use is that Induction lighting is only available in 5000 K Daylight vs. a better 5500-6700 K Daylight, although this is still a viable Kelvin temperature as per PAR especially when one considers the high output delivered with half the heat output. Hopefully the companies that are making these lights will see a market in the Aquarium industry and make them in models that provide the correct PAR needed by corals and plants as these can be a nice rival to the Metal Halide, LED, and SHO!



  11. HID Xenon

    12. HID stands for "High Intensity Discharge", this technology is currently used in high end luxury cars, however there may be aquatic implications here in the future as PAR and other potential issues are worked out. HID lights use an electrical charge to ignite xenon gas (a colorless, heavy, odorless noble gas, which occurs in the Earth's atmosphere in trace amounts) contained in a sealed bulb. The technology of HID automotive lamps is similar to that of common vapor-filled mercury vapor street lamps.

    These Xenon HID lights seem to produce much in the lower chlorophyll A segment of PAR, but currently not as much in the higher infrared part of PAR.

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  • Important Parameters to consider when choosing a light for your aquarium (not a complete list):

    • • Watts per gallon,
    • Lumens per watt,
    • Lumen focus
    • PAR (often easiest determined by Kelvin output), although it is important to note that the symbiotic zooxanthellae found in many corals and clams require more of the "blue spike", so high PAR for higher plants is not exactly the same for corals although it is safe to say a PAR reading of 50 mmol will work for most light sensitive corals.
    • PUR/Useful Light Energy (not wasted in yellow/green light spectrum that green plants and zooanthellic algae reflect)
    • Output in relation to bulb length (this is where LEDs and to a lesser extent T2s and T5s excel).
    • Lux, I generally only consider this parameter in deeper Reef and occasionally deeper planted freshwater aquarium to determine if I am getting the proper light where it needs to be.
    • Specimen Placement/ Tank Depth; although not a parameter per say, it still affects lighting decisions and even the few "watts per gallon" generalizations I provide in this article.
    For instance any SPS/LPS coral placement deeper than 18-20 inches should rule out most T5 lights and deeper than 24-30 inches rules out many LED lights (24 to 30 inches at least requires the most powerful LEDs such as the AquaBeam 100 Ultra or Orphek); In these deeper depths the Metal Halide is still king

    The watts per gallon is part of the lighting equation as stated above is highly inaccurate when taken by itself, yet may in the aquarium hobby industry still go by this outdated generalization which leaves me scratching my head with all the advances in lighting technology. Taken together, the first FIVE points are the most critical (which does include watts per gallon), but no one of these should be a sole determiner of the lights.

    Even a 105 watt Super High Output (SHO) which is an excellent light, especially for planted freshwater or hydroponics applications, when compared apples to apples to the 30 watt GroBeam 1000 Ultra only produces 85% of the same useful light energy despite using more than triple the energy.
    This is not to say the 105 SHO is not a good light, far from it, especially when one considers the vastly lower price and that this SHO light still out produces most any T12, T8 and T5 (using 6500K for all comparisons); as a generalization (assuming equal Kelvin) the SHO requires only 2 to 2.5 watts per gallon for a "high light planted aquarium".

    Using the high end TMC or Orphek LED Lights as a Comparison:

    * 20 watt T12 light with a Kelvin temperature of 5000 K,
    Compared to a:
    *20 Watt LED with an adjusted Kelvin temperature of 6500 K.

    The "watts per gallon rule" would certainly require at least four of the 20 Watt T8/T12 grolite while this same 20 gallon freshwater aquarium would only require ONE 12 watt TMC GroBeam 500, this is .15 of the required wattage or about .60 Watts per gallon.

    For reef applications using high end LED emitters only, not Marineland Single or Double Bright, Ecoxtic Stunners, etc., I would suggest about .8 to 1 watt per gallon; so two AquaBeam Reef White LEDs would be my suggestion for this 20 gallon aquarium (generally speaking, four high end 12 watt LED Light fixtures such as the AquaBeam Reef White 600 would work well for a 60 gallon reef based on this example). Of coarse the differences can vary, so even this comparison only works for the described lights and tank, this is also based on the newer Cree XR-E & XR-G Power LED emitters employed by TMC (and similar proprietary emitter bins developed by Orphek as well as some PAR 38 LEDs) which have a high output of useful energy.

    In fact based on raw data from controlled tests, even the modern comparable Kelvin HO T5 lights or Metal Halide which are so popular do not hold up in comparison to a modern LED with the Third Generation AquaRay LED emitters. This data indicates that a modern LED requires 14-28% of wattage for the same useful light energy output. Even then a T5 or even more so a T2 are vastly superior to the older style aquarium lights when all criteria are applied (SHO as well are also superior).


    Note: Regular readers of this article will note that I changed/simplified my above formula. While the previous formula was always intended as an example (not a hard & fast rule/equation) and those that read this entire article in context could easily figure this out; however one of my aquarium/reef professionals who regularly proof reads this article could see how a reader could take this out context if they were to not read this article in full context (as I pointed out to him as per one extremely rude & condescending email). So as per his suggestion, I removed this formula and replaced it with the above suggested more simplified example of why the "watts per gallon" formula does not apply to most modern aquarium lights.


    Changing bulbs:

    With the exception of LED, most aquarium bulbs go through what is called a half life whereby they are at 50% output. This generally happens around 6 to 9 months in time with normal usage however with lower usage (say 8-10 hours per day) this can be stretched to 12 months.

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    Lighting Time

    Here is a summary of lighting requirements for different aquarium types. I recommend timers for any aquarium to provide good daylight/night cycles, however this is even more important with Planted Freshwater and Saltwater Reef or Nano Reef tanks. Turn the actinic lights on about one to 1/2 hour ahead of the daylight bulbs and one to 1/2 hour later in the evening. I generally have the brightest lights on for about 12 hours per day. Sometimes with MH I will have them in a third cycle that is on for only abut 10 hours or less. I would run moonlights for about 14-16 hours (some prefer to run these 24/7, however I have yet to find in benefit from this that can be scientifically proven other than aesthetics).


  • Light (lamp) Placement:

    • Pendant vs. Canopy with Reflector (Mirror, Aluminum, Mylar)
    The advantage to a pendant reflector over a canopy with reflective backing (mirror, aluminum or mylar reflector) is that it will radiate downward in a slightly more magnified fashion than a pendent reflector, however the reflector/mirror has one advantage over the pendant and that is more wide spread light distribution. A pendent (such as an SHO or Metal Halide) or LEDs hung on rails over an aquarium allows for an open tank which allows for more light energy to reach the tank. The negative is evaporation and possibly aesthetics (which of coarse comes down to opinion).

    If lights are placed in a canopy (which in my opinion looks better) it is generally best to keep a lid on the tank to prevent too much moisture from building up inside the canopy which can also damage lights. I recommend venting the canopy and adding a small fan in at least one of the vents aimed to push air out. This will help cool the inside of the canopy/hood and, just as importantly, help expel moisture. With low heat lights such as LED and T2s, this is of less importance especially for heat, but still helps protect lights from moisture damage.

    The use of a reflector such as mylar (even heavy aluminum foil can work, although it tends to degrade from salty moisture over time in my experience) protects the canopy wood from heat and is useful for directing light downward, especially if SHO, T2, T5, or Compact Fluorescent lights are used. BTW, my first choice is Mylar for both reflective properties and longevity. Please the picture in the T2 Light section of this article for a canopy using Mylar (see this website as one many sources for Mylar; Mylar).

    The use of lids (glass in particular) does block light energy and gets buildup quite quickly under the lids (although lights exposed to open tanks need to wiped clean often too), however the choice of lid can minimize energy loss (see the section lower in the article under Marine Light Summary for more about lid choices).

    So this choice comes down more to aesthetics, space, personal preferences, tank arrangement of plants or corals and more.


    Light Penetration

    What is often a bigger issue, especially with deep tanks (over 24 inches) is to allow as much of the blue light (which is found as part of the light spectrum of high PAR Daylight 6400 K lights) as possible through to the tank and often a glass top will block these light rays (over 60%) so using polycarbonate or no lid at all may do more for effectiveness than whether you use a mirror or pendent (see further in this article for more on this subject).

    As well for tanks over 24 inches the use of some higher Kelvin in your light "mix" may be necessary for coral tanks or in some cases high light requiring plant tanks (depending upon the environment being replicated, as a high tannin, often shaded Amazon River tanks would not require the light intensity and higher Kelvin output of a Reef Tank).
    The use of 14,000 K MH (or even higher Kelvin 20,000K MH) or AquaBeam Ultra 1000 Marine White LED in a mix with High PAR 6400 K SHO lights may provide the "mix" necessary for deeper freshwater tanks.
    For Marine, even in tanks under 24 inches, the use of actinic blue lights may help provide the correct PAR to specimens lower in your tanks water column; a LED Reef Blue 50,000K may help provide this (this LED along with the Marine Blue is also excellent deeper tank penetration).

    Here is the general light spectrum absorption of water:
    • Only 73% of the surface light reaches a depth of 1 centimeter (less than a half inch)
    • Only 44.5% of the surface light reaches a depth of 1 meter (3.3 feet)

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    Specimen Placement


    This is an important consideration that is often missed or not enough weight is given to this part of aquarium lighting and aquascaping

    Reef: Another important point that is often missed by many reef keepers (usually newbies) is even with newer technology high output lights (such as a MH, LED, HO T5, T2, or SHO), specimen placement can make or break a good light system.

    As per the previous section as to general light absorption of water, I would move corals as high up in the water column as possible, this is especially important with SPS corals (short polyp stony corals) where placement on the rocks directly under your lights is even more essential. This is not as essential with LPS corals (long polyp stony corals) since they are more commonly found in near the sandy lagoon bottoms.

    Sometimes in conversations with reef enthusiasts that are questioning different lighting systems/ideas is that it is often missed that the most high light requiring corals (such as SPS) do not grow 100 feet (30 meters) below the surface in the reefs and that these corals will be just below the surface, so regardless of the lights you choose, placement is extremely important. Even less light demanding tropical reef building corals species are restricted to the euphotic zone, the region in the ocean where light penetrates to a depth of approximately 230 feet or 70 meters (there are cold water corals that grow in deeper water, however these are not the reef building corals kept in aquariums that secrete calcium carbonate).

    I should also note that with SPS corals in my own experience, that placement low or even in substrate that I have observed the corals getting "eaten away" by bacteria from the bottom up; while this is an anecdotal observation of mine (as other factors were not tested in a controlled scientific study), it is still consideration in coral specimen placement. The bottom line is that you can have the best lighting system that money can buy, but poor placement of specimens can make it all for not.

    Another thought as marine tanks in general, is to consider what type of environment you attempting to duplicate; for instance a Reef Tank set up to duplicate the Great Barrier Reef would require aquascaping and higher power lighting to best replicate this environment. While a marine tank set up to replicate the much more turbid waters off the California coast would not require the same aquascaping or as high power of lighting.


    Freshwater: If your lights are for Freshwater plants I would move the high light requiring plants directly under the lights (I generally elevate them with terracing, which can look quite attractive if done well and serve a dual purpose of aesthetics and better light energy absorption).

    As with marine tanks, consider the environment you are replicating; for instance an Amazon River environment aquarium (with fish such as Discus) are full of tannins and have many shady areas and so one cannot compare the lighting needs of a tropical reef with the Amazon River. More light and dark spots should be utilized so as to provide a more natural and comfortable environment for your aquarium inhabitants, as well the same intense lighting for the same size Tropical Reef tank should not be used for an Amazon River aquarium of the same size and depth.


    • IMPORTANT- Another point about lighting in general is that higher wave lengths of light such as UVA do not penetrate glass well or even acrylic. I recommend direct lighting (best), quartz or polycarbonate where UVA is essential. Just make sure to clean your bulbs or polycarbonate tops regularly to prevent build up that will block light.
    Even though infrared will penetrate glass, it will not penetrate dirty glass with algae or hard water deposits on it, so keep your aquarium cover clean for any tank where lighting is important such as FW plants or Reef Aquariums.

    Here is a very basic breakdown of UV blocking potential:
    *Glass- about 60% of UV will be blocked
    *Acrylic- about 40%
    *Polycarbonate- about 8-10% (this is what I used when a lid was necessary)
    *Quartz- about .5-2%

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  • TANK SET UP LIGHTING SUGGESTIONS:


    • Please note that I have received many requests for exact recommendations of lights for certain aquariums. I prefer to not give these as there are too many variables which then will make my advice anecdotal, as with Aquarium Medications, Chemistry, & similar subjects I prefer to give as many tools for the aquarium keeper to make an educated decision on his/her own. As well since Lighting is a fast changing part of aquarium keeping, a recommendation I make today may be less accurate in a year (or less).

    As a guide I will make a few suggestions in the following sections, however please take these as suggestions, not something written in stone. Please consider all I have written up to this point, your personal aquarium parameters, inhabitants, budget (which is always important), & more when deciding what lighting systems or combinations there of to use.


    Penn Plax Aquarilux aquarium lights • A BASIC FRESHWATER FISH TANK (including some low light plants) MAY not need as much lighting and will often do OK with one "Aqua Glo", "Color Max" or similar (30 watt) light for a 60 gallon aquarium.

    A 6400 K Power Compact is also an excellent basic freshwater and inexpensive tank lamp. Please keep in mind that even though "Aqua Glo" and "Color Max" produce some PAR, they do not have the output (lumens per watt, lux) for any thing more than low light plants.
    Other basic but "a step up in lights" are the ZooMed and Coralife Trichromatic as well as the ZooMed FloraSun and VitaLite. There are many others that have reasonable outputs in the 5500-8000 Kelvin range.

    It is worth noting for even a basic freshwater aquarium that better lighting will usually result in healthier fish and easier control of algae, especially Brown Diatom Algae. Higher PAR lights may have an effect on Redox which directly impacts fish health, absorption of nutrients, and general disease resistance of fish. Unfortunately for many basic freshwater aquarium hobbyists, commonly sold aquarium bulbs do not publish anything other than "aquarium light that brings out fish color".

    Besides the before mentioned Power Compact lights, the T2 lights are excellent lights that have good PAR for health, plant growth, less Algae. These can also be linked for larger aquariums which make for a one size fits all first rate fixture.
    Please AVOID the incandescent standard aquarium light that are still sold in many aquarium supply retailers (please consider substituting CFL lamps mentioned earlier in these fixtures!)

    *As an example, with a 36"L x 15"W x 16"H 40 gallon aquarium I would suggest (2) 11 or 13 Watt 6400K T2 Lights as a good set up for a basic freshwater aquarium.

    For further basic freshwater tank lighting information, please see this article (in the Light Basics section): "Freshwater Aquarium Basics, Care"


    • A FRESHWATER PLANT aquarium needs a higher PAR plus more lumens/watts of light. Photosynthesis takes place at the blue end and especially at the red end of the Nanometer curve (420-485 nm blue and 670 nm red). This area of peak photosynthesis is referred to as "PAR" as discussed earlier.

    In aquariums where you cannot or do not want to have multiple bulbs, an approximately 6500 K bulb works best most planted tanks (tanks deeper than 30 inches may need higher Kelvin outputs, however this will also sacrifice some of the high percentage of PAR found in a 6500K daylight).

    In smaller aquariums I now tend to use the economical Power Compacts with 6400-6700 K Daylight (which tend to be full spectrum as far as green plant growth is concerned. An excellent bulb for low to medium light requiring planted tanks and that will fit in a standard socket is the 6400K, 15 watt Fluorescent Daylight bulb for aquariums. This is a great economy/starter plant and fish light; this bulb fits any standard incandescent fixture and is an inexpensive way to turn an incandescent hood into a power compact light fixture useful for plant growth in small aquariums!


    For a step up in smaller tanks, the T5 and especially the T2 in 6000 to 7000 K range are good choices. The T2 Fixtures (pictured to the left) can be mounted in a hood, placed on or above an aquarium, attached end to end to make a long fixture or overlapped, making these a versatile plant capable fixture for tanks as large as 75 gallons (not suggested for tanks deeper than 18 inches for planted/basic reef tanks).


    For larger Aquariums (over 60 gallons) I recommend the newer SHO (Super High Output) 6400K Bulbs, high output lamps. Quite bluntly I have not seen a better plant light as of writing this (which is why they are also popular in Greenhouse/Hydroponics use).

    The "new generation" LED Aquarium Lights which can be purchased in Natural Daylight Configurations for high end, long life, low energy applications are unmatched in output/growth versus power consumption. The PAR 38 6500K Spotlight LED can also be used in high light areas (this light is very popular for Hydroponics for intense light in a small space).

    Since plants use both green and red light for growth, the use of full spectrum daylights are useful for healthy green plant growth. I have seen it mentioned & observed that blue actinic light will encourage certain algae growth. The blue light encourages all green growth, both plant and algae, so if the plants can out compete algae based on other parameters this generally is not an issue. I have observed (as well as heard from others) that Black Beard Algae (BBA) is more common in tanks where actinic lights are employed, admittedly this is by non scientific observation, but I would consider using only 5500 to 8000 K lights if this is a concern.

    A final note as to freshwater plants, is that the more light (in correct PAR) you add, even in low light plants, the more the plants will require additional nutrients; in particular carbon. This can be provided by fish respiration, products such as Flourish Excel and CO2 generators, however in medium to high light plants you will likely need to supplement CO2 in some form or another.
    Please read this freshwater aquarium plants article for much more about this subject:
    "Planted Aquariums"

    *As an example, with a 36"L x 15"W x 16"H 40 gallon aquarium I would suggest (4) 13 Watt 6400K T2 Lights as a good set up for a medium/high light planted aquarium, Or (2) 65 Watt SHO or (2) GroBeam TMC LED lights for a high light planted aquarium (of course combinations of lights and other variables apply).
    (2) 65 watt SHO Lights would provide excellent lighting for "high light" demanding plnats and although these lights require a bit more DIY ability, for the price there is no better planted aquarium light (the SHO is also available in a 85 & 105 watt model too)



    • A BASIC SALTWATER or FOWLR tank also does not have as high of requirements, as but more than freshwater (especially if you do not want too much brown algae). A "Coralife 10,000 K" or "Hagen Power Glo" are reasonable (but very outdated) basic saltwater lights.
    The Newest Generation T2 Fixtures are an excellent choice for smaller aquariums or even larger aquariums when the T2 fixtures are connected together. For smaller tanks the 6400 K CFL lights make a good choice and the SHO for larger aquariums.

    Finally and although pricey, an LED is still worth considering especially when you consider the 50,000 hour life, and high usable light energy output.
    Recent research in humans can also be extrapolated to a fish only tank. The research shows good lighting can improve health and increase disease resistance; for this reason a T2, SHO, or LED are worth considering over a 1980s style "Marine Glo" T12/T8 light.

    *As an example, with a 36"L x 15"W x 16"H 40 gallon basic marine aquarium I would suggest (3-4) 15 Watt 6400K/Blue T2 Lights (other combinations of lights and other variables apply). One TMC AquaBeam Reef White, Marine White or Marine Blue can easily light a 40 gallon fish only/FOWLR marine aquarium as another alternative.


    • A BASIC REEF OR NANO REEF (low light Anenomes, Tube worms, etc.): In a 10 gallon Nano Reef, two Power Compact bulbs will usually do well.

    A step up would be T5 light fixture or a further step up would be the new 6400K, Actinic T-2 Lamps/Fixtures which are a good compliment to a Pico or Nano Reef due to their compact size and high lumens per watt output and are now my choice for these tanks along with TMC or similar HO LEDs. These fixtures can also be mounted in parallel and/or snapped together end to end for larger aquariums with higher output needs.

    Finally the VERY new AquaRay LED Light systems can be used alone or in combination with T2, T5, CFL or possibly SHO lamps for Basic Reef or Nano Reef Tanks. Generally I recommend the Aqua Ray combined with the T2 6400 and/or Blue fixtures in tanks under 60-75 gallons (or even larger if linked) or the T5s for larger tanks.

    *As an example, with a 36"L x 15"W x 16"H 40 gallon aquarium I would suggest (2) Reef White TMC LED lights or (2) 6400 T2 & (2) Marine Blue TMC LED for a basic reef aquarium (of course combinations of lights and other variables apply).
    For even more light, the new TMC XG AquaBeam 1500 or newer yet TMC XG Ocean Blue 1500 would produce copious amounts of useful light energy with their small foot print, yet high output and light spread.
    *Another example with a 60 gallon hex aquarium, I would suggest the more compact TMC AquaBeam 1000 with more than double the output of the TMC AquaRay/Beam Strips in a more compact space (for longer tanks, the LED strips are generally still more practical).


    • AN ADVANCED REEF with hard corals and other photosynthetic reef inhabitants such as Maxima Clams which obtain their primary source of energy from light and then also actively feed to obtain more energy, these may need several or a combination thereof Metal Halide and Marine Reef LED, SHO, T5, or CFL bulbs.
    Keep in mind (as per the PAR/PUR sections of this article) that the symbiotic zooxanthellae require much more of the approximately 465nm blue light energy than "higher" plants, so the use of higher Kelvin white for better daylight penetration and blue lights is generally necessary.

    If LEDs are desired; the TMC Reef White, Marine White, Marine Blue, or even Reef Blue AquaBeam 600 LEDs, along with the AquaBeam Ultra 1000s (for even more intense bright spots especially in deep tanks, similar to that of a 175-250 Watt 14,000-20,000K Metal Halide) would make for an excellent high end application for Reef Tanks under 30 inches in depth.
    For Reef tanks under 20 inches in height (such as a 60 gallon standard), the new AquaBeam XG 1500 Ultima and TMC XG Ocean Blue 1500 have a extremely high output useful light energy from a small footprint yet large light spread fixture (two of the Ocean blue 1500 would provide unsurpassed lighting for a 60 gallon standard aquarium).
    As a generalization for tanks under 24-30 inches; approximately .8 to 1 watt per gallon of High Output Only LEDs can be used for advanced Reef tanks (this does not apply to the many low output LEDs available from Marineland, Current, BaiSheng, Blue Moon Aquatic, E.Shine and many others).

    In a large Advanced reef aquarium combinations of lighting systems may yield your best results and also possibly alleviate the need for expensive and often unreliable chillers. For example, in an 8 foot 200 plus gallon advanced reef tank 4-6 AquaBeam Reef White 600 LED and Marine or Reef Blue LED & 3-4 AquaBeam Ultra 1000 over the most light sensitive clams and sps corals. T2 or T5 light strips could be substituted at about 3 to 1 for the AquaBeam 600s. Another possible lighting arrangement is the use of about four 85 or 105 SHO lamps mixed with a couple Marine or Reef Blue LED and a AquaBeam Ultra 1000 or Metal Halide over the most sensitive corals. With this configuration, the best way to install the SHO light is suspended over the aquarium them in a slightly staggered parallel (utilizing the SHO reflector for this application would be optimum).

    *For tanks over 30 inches of depth (& some tanks over 24" with deep specimen placement), the use of 14,000K- 20,000K Metal Halides at least in part is still strongly suggested. While the TMC AquaBeam 1000 Ultra compares well with a similar Kelvin 175 to 250 Watt MH, this comparison starts to fall off at 24 inches of water and is notably a poor comparison over 30 inches of water (less than 12 inches of space between these LEDs and the tank water/top is also suggested for optimum performance).

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  • SUMMARY:

    • The reader should note from all the information written above, that when deciding what lighting to get for your aquarium that the watts used is only one third or less of the equation in deciding what lights, what size and how many should be used. I will admit that I still will use the watts per gallon as a starting point; however specimen placement or tank depth, lighting type strengths and weaknesses must be considered too.
    I have made several watts per gallon generalizations throughout this article, but these are meant as "apples to apples" comparisons (High Output LED to High Output LED, T5 to T5, etc.), not apples to oranges (such as SHO to T12, or High Output LED to low output LED such Marineland LEDs)

    Please note that besides years of personal fresh and saltwater keeping experience, MUCH more of this information I have written here comes from research OUTSIDE the aquarium industry. Much of what I have learned (and I am STILL learning) comes from this constant research of as many lighting tech research as I can read often from horticulture or other outside sources as noted earlier.

    Some examples include the lack of information in the aquarium industry/hobby that must be found elsewhere includes the SHO or T2 lights that are often superior to more commonly recommended bulbs in the aquarium hobby, yet in much better funded lighting and horticultural industry literature/information these lights are much better known.

    There is also good evidence that correct lighting benefits ALL fish as well, including salt & freshwater fish. I have observed better disease resistance in marine fish in loosely controlled studies when lighting is upgraded to higher intensity, high PAR lights. Proper lighting may play a role in nutrient assimilation, improved Redox, lower incidence of Brown Diatom Algae. Studies in humans that show an impact of lighting on health, may have strong implications for fish (this may be a factor in my studies that showed higher disease resistance when lighting is improved).

    Lighting that as closely duplicates the sun (not necessarily light that is most pleasing to us) is important for ALL life, although more noticeably for corals and plants. Fish too are part of this chain of life. Basically if you take away the sun and the energy it provides, you take away life itself and I do not think if you are trying to achieve the best environment for your fish whether fresh or saltwater, you are doing them a favor by depriving of this source of energy, so duplicating this is one more part of your "aquarium keeping puzzle" (see "Aquarium Disease Prevention"). I should point out that obviously, some fish prefer subdued light, but this is easily handled by hiding places, caves, plants (live or artificial), products such as Peat or Indian Almond Leaves that "color" the water, and simple placement of lights where as some areas of the aquarium are better lit than others with plants/corals placed in way that benefit the most in these areas.

    Please click on the link below for a pdf downloadable web page of this article, this can be saved to your iBooks, Computer, etc.

    Aquarium Lighting; pdf (as of 12-27-11)



    References (there are many more scattered within this article):

    *"WHY IS WATER BLUE"

    *"FACTS OF LIGHT- Color Temperature (Kelvin)"

    *"THE KRIB- Aquarium Light intensities comparisons "

    *"AQUA BOTANIC- A Comparison between Light Sources Used in Planted Aquaria"

    *http://www.ledgrowlights.com/

    *http://www.uky.edu/~jholl2/technology_pdfs/KelvinColorTemperature.pdf

    *http://micro.magnet.fsu.edu/primer/java/colortemperature/index.html

    *http://www2.chemistry.msu.edu/faculty/reusch/VirtTxtJml/Spectrpy/UV-Vis/spectrum.htm

    *http://www.advancedaquarist.com/2008/12/aafeature1

    *The Staff at Quality Marine USA for their expert input and Lighting knowledge to this article

    *American Aquarium Design and Maintenance as well as many other Professional Aquarium Maintenance Companies for their input and test results that went into this article as well as help with CONTINUOUS Updates!!


    For more about my "how" and "why" of my article writing: "Aquarium Information"

    For more aquarium information and articles (pond too), please visit this site:


    Aquarium Information

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