AQUARIUM LIGHTING, Guide to Complete Facts & Information
Written with professional experience & research since 1979.
This is an depth 'aquarium light info' article with basic & advanced applications that is regularly updated.
When choosing your aquarium lighting, there's MUCH MORE to consider than just "WATTS PER GALLON". Back in the days of buying your fluorescent cool white or warm white T12 or T8 lights (often even at hardware stores), this 'rule' was quite accurate and useful since we were more comparing "apples to apples". Often this would range from 3 to as much as 5 watts per gallon, but this now is quite outdated for most modern lights.
In fact, the Watts Per Gallon is a VERY basic start, as this "rule" varies depending upon what is kept, what type of lighting, etc. This is a very general rule and quite out-dated due to the variety of available modern lights with varying lumens per watt, different wavelengths, focused lumens, PAR, PUR, PAS, & RQE.
One cannot simply compare one light to another anymore and use the "WPG" rule, even within the same lighting types as there is often much variance.
If you are TRULY interested in the "BEST AQUARIUM LIGHTING", Please read this ENTIRE article to understand ALL parameters necessary for your aquarium light determination.
There are other factors affecting lighting for your aquarium.
Other aquarium lighting considerations, besides energy input (watts) used are PUR, PAR, Lumens per watt, and even output relative to the size of the light.
Water penetration is another consideration. 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 they naturally reside in.
This overview is just a brief explanation of aquarium lighting.
For cynical readers of this article who claim I have a bias; obviously I do, but then this is based on much research and use.
As a BRIEF generalization, we are first concerned with INPUT energy, then OUTPUT energy. This can be further simplistically broken down into these 6 considerations:
Finally, it is still worth noting that even our best man made lighting is still far inferior to sunlight. So short of placing our aquarium outdoors, all we can do is attempt to emulate at least the most useful aspects of sunlight energy that we can.HERE ARE THE IMPORTANT FACTORS IN DEPTH;
1: KELVIN RATING (such as 10,000K daylight bulb):
What is meant by 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:
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.
A few notes about Kelvin:
What Kelvin rating for Plants & Corals;
http://micro.magnet.fsu.edu/primer/java/colortemperature/index.html Color Temperature in a Virtual Radiator- This is an interesting resource worth checking out.Kelvin Color Temperature
Mixing Primary Colors
This is a fun/interesting online tool!
2: THE NANOMETER RANGE (SPECTRUM)
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 photosynthetic marine 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 (over 22 inches) and/or supplementation with more blue lights (400nm- 490nm).
See the picture to the left that shows a T8 5500 daylight aquarium light that is commonly sold, this graph clearly shows the less efficient green/yellow energy as well as the incorrect spike in orange rather than the correct PAR spike in red 630+ nm
It is also noteworthy that many "terrestrial plant lights" as well as many aquarium plant lights (often of lower in kelvin temperature) have more "red nanometer spikes" than higher kelvin 6500k, 10,000k & higher lamps.
A measure of the intensity of light (referred to the photometry of light), one lux is equal to one lumen per square meter. This is another area of comparing apples to apples in lights, not just watts.
While this measurement only includes light visible by humans, this can still be a useful tool for freshwater plants & most corals in marine reef aquariums.
PAR is an important and accepted starting point to estimate light energy, but should NOT totally override the also important related Useful Light Energy (PUR which literally stands for Photosynthetically Useful Radiation). We measure PAR via µMolm which is a unit of measure (more about measurement later).
PAR is the abbreviation for Photosynthetically Active Radiation which is the spectral range of solar light from 400 to 700 nanometers that is generally accepted as needed by plants & symbiotic zooanthellic algae for photosynthesis (Zooxanthellae are single-celled algae that live in the tissues of animals such as corals, clams, & anemones).
UVA to 550 nm contains the absorption bandwidth of chlorophylls a, c˛, and peridinin (the light-harvesting carotenoid, a pigment related to chlorophyll). The photons of light energy within these spectrums are more energetic and by themselves tend to provide more plant growth
Lights that produce light under 500nm will produce a lower PAR reading for a given energy input (wattage), not because less energy is emitted, rather because most PAR meters are less accurate below 500nm.
*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.).
*Photosynthetic response; During this time, the molecules needed for photosynthesis gradually reach operating levels which begins when energy from light is absorbed by proteins called photosynthetic reaction centers that contain chlorophylls.
*Chlorophyll synthesis; occurring in chloroplasts, this is the chemical reactions and pathways by the plant hormone cytokinin soon after exposure to the correct Nanometers wave length , that traps the energy of sunlight for photosynthesis and exists in several forms, the most abundant being Chlorophyll A.
*Chlorophyll A; A type of chlorophyll that is the most common photosynthetic organisms predominant in all higher plants, red and green algae higher plants, red and green algae. It is best at absorbing wavelength in the 400-450 nm and 650-700 nm
*Chlorophyll B; The chlorophyll that occurs only in plants and green algae. It functions as a light harvesting chlorophyll pigment that pass on the light excitation to chlorophyll a. It absorbs well at wavelength of 450-500 nm and 600-650 nm
Further PAR Information;
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 & PAS output.
As an example, just within the same brand of emitters; using the same energy input of 12 joules (watts) at 400mm we know the measured µMolm of the CRee XT-E Fiji Blue is 38 µMolm while the CRee XB-D 6500K Natural daylight is 61 µMolm
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 PUR range required by plants, which is why Cyanobacteria thrive in lighting conditions that include more yellow light energy.
5: RQE, PAS, & PUR, "Quality of Light"/ "Useful Light Energy":
Another term is Photosynthetic Action Spectrum (PAS). I should point out that while the terms PAS & PUR have a lot in common, there is a difference in that PAS is most simply stated as the spectrum where "chlorophyll is much more efficient at using the red and blue spectrums of light to carry out photosynthesis. Therefore, the action spectrum graph would show spikes above the wavelengths representing the colors red and blue."
While PUR also encompasses this too it also can simply refer to all light spectrums within PAR with emphasis on the more efficient spectrums rather than the less efficient spectrums such as yellow and green. Or stated another way, the portion of PAR, which is more efficiently absorbed by plants & zooxanthellae photopigments thereby stimulating photosynthesis. We can state PUR one more way, where as PAR is the most important quantity of light, "PUR is the quality of light as per application".
The picture above depicts both full solar radiation that reaches the earth as well as how a few different man-made light sources fit into the visible/PAR aspect of this spectrum.
The other term that is thrown around is "Quantum efficiency"; this term generally refers to the efficiency to incident photon to converted electron (IPCE) ratio of a photosensitive device which predicts a 30% lower efficiency in green spectrum (see diagram in PAR section).
There has been a lot of confusion about this subject, especially when considering LED lights, as many sellers and aquarium keeping personalities with little background such as "Mr. Saltwater Tank" will hype high PAR values while ignoring PUR. Often terminology is confused or "Red Herring" type arguments are made to confuse the subject, but regardless of what you call it by, we have had a general knowledge of PUR, RQE, and PAS for some time.
Many people will think PUR is good in theory, but think it cannot be applied to every single species we are trying to grow under water. While we don't know every species and it's preferred nm of light prefers, we do know the light, which triggers photosynthesis in an organism as well as efficiencies based on real world tests.
Another misapplication that is often applied in certain aquarium keeping cicles where they have apparently not done their research into the history of aquarium lighting as per PUR is to compare a high PUR light to a lower PUR light of much higher input wattage.
A little history: since I have been in the industry on the research and aquarium system design side since 1978 (longer if you count my basic hobby years). I have called this subject "useful light energy" since at least 1985. Then, I read elsewhere that the more scientific terms of PUR, RQE, & PAS. All this said, the only term I personally made up to best explain to my clients, which paid for my service was "useful light energy". This explained it well, based on feedback from clients and others in the industry despite others attack upon this term. Frankly a new term that I have heard thrown around that I think is less vague would be "Quality of Light per Application".
The ability of newer technology lights to pin point the exact nanometer spectrums needed for PUR in output results in much less wasted energy and allows for a light of considerably lower wattage to actually out produce another light of higher wattage.
Since it is well established that a photon is a photon and it is the quantity that certainly makes the most difference (PAR is quantity), we still cannot ignore the quality of the photon of which the only difference of a photon is the wavelength and frequency (energy).
For a further explanation, please read this article:
Reference also cited for this explanation: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3975419/
The picture to the left demonstrates this with two 15 Watt CFL (30 watts total) vs. one 3rd generation 12 Watt Marine White LED (daylight 14,000K).
The picture below shows a spectrograph of two 6500K aquarium lights. One is an AquaRay GroBeam and the other is a 6500 Aquarium CFL. The LED is rated at 12 watts while the CFL is 13 watts.,p>
While similar, it is clear to see the LED has more blue and a lower blue NM (fuller blue spectrum) amount as well as more red, less green and, the same yellow.
A Couple more points to better explain the concepts of PUR, "Useful Light Energy", or "Quality of light per application".
b>For further reading about PUR:
This is another concept to consider that we do not know all the "mechanisms" that drive it.
The implications for us as aquarium keepers is this process can often be the result of new light systems until our plants, photosynthetic corals, etc. adapt to the new light.
Further Reference/Reading: Wikipedia; Photoinhibition
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.
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!
The term "watts per gallon" is getting more archaic with the newer T-2, T-5, CFL, the SHO, and especially the new reef compatible LED lights.
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.
CRI is useful in specifying color if it is used within its limitations. 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.
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! However many low end aquarium lights such as the Fluval LED Lights still refer to CRI since their PAR & in particular, PUR is poor.
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AQUARIUM BULB TYPE:
Aquarium Light Types Explained Here Include:
A standard pin, 1-1/2" wide bulb. The main caution to the use of these bulbs for aquariums, 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).
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), making the T-8 a more efficient lamp than the T-12.
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.
• 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 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.
Another consideration for higher output requirements, such as large planted freshwater aquariums, consider the in terms of performance and cost SHO light over the T5.
Since I have seen a wide variance in quality of build as well as quality of output similar to with LED lights, I recommend going with the best and for this I would recommend the premium Giesemann T5 lights which have unique phosphor blends that are characterized by exceptionally high output performance, long life span, consistent coloration combined with high levels of spectral stability over time. In other words both quantity (PAR) and quality (PUR) of light.
These bulbs are the latest fluorescent technology yet.
Quite bluntly, these T2 lamps and fixtures are about the best fluorescent lamps 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).
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.
The Aquarium above is a planted 10 gallon with two 11 Watt T2 fixtures
Freshwater Planted Aquariums
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 have, 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.
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) was 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 generation T2s we are now using do not have this problem based on considerable use.
*VHO Power Compact
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 T6) lamps such as the Current USA, Coralife Quad & Via Aqua Helios VHO.
Coralife has a quad lamp VHO (such as the 20 inch; 96 watt fixture) that have high output in small space.
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.
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 is not as good as T2, SHO or especially LED Lights, which the LED in my tests, feedback, research and experience are the future of aquarium lighting, especially as it pertains to freshwater plant and reef aquariums.
*SHO Lights, Lighting
*Premium Aquarium LED Lighting
*PC (or CFL);
This 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).
*SHO Power Compact Lights:
A newer Power Compact that in my opinion is awesome for planted aquariums or hydroponics, in fact the best other than some high end LEDs and at least equal or better than most T5s for planted freshwater aquariums. As well the SHO can be used for reef aquariums (as an addition to LED or Metal Halide)
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.
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 an optional 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 super high output aquarium lighting. This is especially true for planted freshwater aquariums when cost is considered since these lamps do not require expensive ballasts like a MH (SHO are self ballasted) and generally cost $30 and up per lamp.
See also: Aquarium Plant Care, Information
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 high output LED Lights (such as TMC Reef 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.
The 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.
The picture to the right 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
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).
*Metal Halide (MH);
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 in many aspects of aquarium lighting).
*LED (light-emitting diode):
These LED lights have the same shimmer effect and "popping" of coral life otherwise found in Metal Halide.
The difficulty in the past is correct wave length of the emitters, which in part are affected by the drivers/circuitry maintaining correct voltage over all emitters.
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 top manufacturers of LED fixtures become more readily available as the price comes down, while at the same time PAR & PUR (quality of light) & general aquarium compatibility come up.
Since LEDs emit light only in a very specific direction, the installer also has the option to illuminate a precise area using lenses in specific degrees of angle.
Achieving the correct wavelengths in the correct amount 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 some of the less efficient light spectrums can be omitted with correct emitter bins and proper drivers/circuitry.
An example of a new emitter developed just for photosynthetically sensitive reef inhabitants is the 'Osram Olson NP Blue'. This patented emitter primarily targets the FULL spectrum of blue necessary for phototropic response, as well it also contains light energy in the full spectrum of PAR, unlike other blue emitters that have come before it.
Another problem with many low end LED fixtures is even if the emitters used are of reasonably efficient bins, these LED fixtures "daisy-chain" their LED emitters together rather than provide the expensive drivers/circuity needed to maintain exacting voltage to each emitter. A plethora of LED fixtures are made in the same Chinese factories using the same lower "hardware store LED technology" under multiple brand names and sold at many aquarium stores and online big box sellers.
As well "pulse width modulation" (PWM) is best used for controlling the dimming of these emitters so there is no change to the spectral output as opposed to using "current reduction" (aka “linear or analog reduction”) used by many (most) brands of LED fixtures of which the result again is less than optimal PUR and wasted energy as heat instead of light energy.
As previously noted, this also results in more heat output and often the requirement of fans by these LEDs. This excess heat being driven away by fans simply equals input energy (joules) that is NOT GOING TO LIGHTING YOUR AQUARIUM!
Speaking of fans, besides the wasted energy, these fans make good water-proofing/resistance very difficult. This is why most LED fixtures have a water proof rating of IP66 or less. This means your electronic lighting device is being placed in a wet environment with a risk of failure over time or especially if dropped in the water.
Another aspect to consider is that unlike fluorescent, incandescent, and other lighting types; very specific emitters require circuitry/drivers similar to your computer.
Simply put, the more emitters along with more specific light output requirements, the more complex and expensive the circuitry and thus NO LED fixture is going to have specific output light energy with say 100+ emitters AND be even remotely close in price to one using 10 emitters if both are using correct LED driver circuitry.
The TaoTronics & Fluval are a good examples of LEDs to avoid for this reason if one seeks the highest output of efficient PAR per watt of input energy used, not that these do not work, they just need much more energy for the same results as a high end LED using the best emitters, drivers, & PWM (as well, the warranties of ALL LEDs utilizing lower tech drivers, low water resistance ratings, and "Current reduction" is considerably shorter)
It is also in the area of emitter development where-by development costs are incurred and where many who do not understand the business aspects of these costs, will then question why one LED manufacturer has or can have exclusive patent rights or similar.
Controlled Tests with Plants and The Aquatic Life Implications;
As previously noted in the "Useful Energy Section", tests for plant nurseries (Green House, Hydroponics) full spectrum LEDs such as the newer generation TMC GroBeam Aquarium Lights, 3-10w 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.
Implications of these tests:
Reference: PUR in Aquarium Lighting; Depth 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 should easily replace one 175 Watt Metal Halide MH of similar rating for marine applications.
There are mixed reviews on the older generation larger units such as the Solaris 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.
Video for an aquarium with three TMC Reef White LEDs & two CFL lamps:
Video with a TMC 1500 NP Ultima Ocean Blue (over a 29 gallon aquarium)
Video with reef aquarium utilizing TMC Ultima NPs, Reef White 600 Ultimas, and PAR 38 LEDs:
More about Emitters:
As I noted earlier, not all emitters are equal even with the open source Cree emitters, commonly sold for other applications. These are only as good as their correct wavelength output (Kelvin Temperature/Nanometers). One cannot compare a computer that uses an exclusive patented Intel processor to one that uses maybe a similar, but generic version of this processor. As with a computer processor company, an LED emitter manufacturer is going to have exclusive patents as well as generic versions.
What's noteworthy is the latest licensed version of even the newest Cree emitters (such as the XT-E, XB-D, & ML-E) are not available over the counter to even to the majority of LED builders (including AI, EcoTech, BML) that do NOT have the patent/license rights.
Far worse yet would be the cheaper no name emitters used by manufacturers such as BaiSheng, Epistar, & others sold under a plethora of other names for so-called aquarium use. These use daylight emitters that can vary widely in Kelvin Color output from only 2000K to 6500K and are in reality generally much less efficient for photosynthetic aquarium life use other than just plain light!
Based on email I get, forums I regularly read, & YouTube videos (for DIY LED Aquarium Lights), many seem to make this very INCORRECT assumption about emitters, drivers, PWM, wasted heat energy, etc.
These same older generation emitters, controller technology & drivers are the reason I did not recommend LEDs of ANY brand for "higher-end" aquarium applications until 2008 (readers of this VERY constantly evolving article in 2007 would note this too).
As noted earlier, another common LED emitter usage is "cool white", "warm white", and "neutral white" by many LED manufacturers so as to obtain necessary efficient PAR spectrums and a pleasing color through a shotgun approach. These same LED manufacturers then disguise their LEDs using "cool features" and ramped up input wattage to drive high PAR numbers to sell these otherwise inferior LEDs as per PAR/PUR delivered for wattage used.
Unfortunately good marketing has convinced many, that would never place a "warm white" or "cool white" fluorescent or MH over their reef, that these lights are top notch (which of course simple logic says they are NOT)???
I should also remind readers that when tuning in specific color combinations, this results in 40% or more loss of stated PAR output since not all emitters are running at full potential. HOWEVER, this is not the case of the Aqua-Illuminations Hydra HD since this LED allows the user to drive light colors at more than 100% when another color is turned down (so that 100% of the input energy is indeed utilized).
This said, this does not make these LED fixtures bad, just less efficient using much more input electricity for the same results and often this results is lower PUR spectral efficiency and fixture lifespan (hence the one year warranty of most of these high end lights that perform all these functions).
Another noteworthy FACT (as noted earlier in this article) is the green light energy produced by these fixtures is less useful for Zooxanthellae photosynthesis and these same photosynthetic marine life have adapted to an environment of much more blue nanometer bands of light energy and little red is required nor does it penetrate!
Another misunderstanding about LED emitters is targeting the responsive wavelength. While exact coral responsiveness wavelengths are unknown, much is known in a more broad sense (and even more knowledge is growing, such as the "blue band" of coral responsiveness). For example, we do know that much of the yellow and green bands are 30%-80% less efficient for most photosynthetic corals, clams, etc. (although under 24% green light can be useful, but over 25% it is actually detrimental; Reference: Ref. 1)
This has been a controversial topic in a few fragging circles, when it comes to a few red corals such as Red Acans. I have found little to support the claims that these corals fade to orange under correctly applied LED Lights.
Since many over load on blue emitters, and admittedly most "better" LEDs lack as much of the yellow nanometer light cyanobacteria need to thrive, I feel this (along with specimen placement) is the possible cause and why those who use a good mix of LEDs or even LEDs with T2s or T5s have not observed this phenomenon.
Use of LED to prevent Red Slime
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 (25,000 to 50,000 hours vs. 8000 hours), the modern recent generations of LED Fixtures are generally the best available aquarium light.
Retrofit is also not all that difficult with most better LED systems sold with hardware that makes DIY mounting options quite varied.
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.
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.
Please click on the picture above/left for a larger animated version of the lunar cycle
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.
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Important Parameters to consider when choosing a light for your aquarium (not a complete list):
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) Light" which is an excellent light, especially for planted freshwater or hydroponics applications, when compared apples to apples to the 30 watt GroBeam 1500 Ultima 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".
Lighting Time & Replacement
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.
ANY fluorescent light used for aquarium applications such as planted aquariums or reef, slowly burns up phosphors and other rare earth elements that produce the light energy necessary for PUR.
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