By Steve Allen
Further Revised 1/31/14
Much of the information used with permission from:
AQUARIUM LIGHT; FACTS & INFORMATION
Sections Included in this Article:
Aquarium Lighting Overview
There are many considerations when choosing aquarium lighting, in particular lighting for “high end” applications such as marine reefs or high light planted aquariums.
“Watts per gallon” is still often referred to, however of late this is but one part of many parameters to consider.
This is specially true when high end LED lights are considered (this does not include low end and similar).
An example of a “high end” LED:
TMC AquaRay Aquarium Light Systems
An example of a “low end” LED:
Marineland Double Bright LEDs
Watts per gallon is only useful in comparing “apples to apples” such as similar T5 lights to another or related technology LED lights to another (not a Marineland Double Bright to a high end TMC AquaRay LED).
For a better understanding please read this ENTIRE Aquarium Lighting article which explains that a watt is simply a measurement of energy, NOT light output or even light energy quality:
Aquarium Lighting Information
Even comparable lumen output of the lamp is no longer a good measure of lighting parameter performance due to focus and restrike as well as PAR & related useful light energy (PUR).
A good example is a modern LED such as the Aqua Ray which has a vastly higher useful energy (PUR) output than a comparable wattage CFL (such as a Current USA Compact Fluorescent) at 20 inches.
Important Parameters to consider when choosing a light for your aquarium (not a complete list):
- Watts per gallon
- Lumens and lumens per watt
- Output in relation to bulb length (this is where LEDs and to a lesser extent T2s and T5s excel).
While a minor parameter, it is still worth considering
- Lumen focus (AKA Restrike).
This is common to ALL fluorescent lights, whether modern T2 or T5 or older T12s.
- PAR (often easiest determined by Kelvin output),
- Lux; is derived from the lumen and is a measure of illuminance.
This is the luminous flux hitting the surface.
Similar to PAR & PUR as this is the amount of useable light.
For example, 1000 lumens spread over an area of 1 square meter gives you a figure of 1000 lux, however the same amount of light spread over 10 square meters gives an illuminance of only 100 lux.
In short illuminance is more relevant to lighting an aquarium than luminous flux (lumens) because this is the measure of light that can be applied to your aquarium.
This figure will decrease the further from the light source you get.
- PUR/Useful Light Energy (not wasted in yellow/green light spectrum that green plants and zooanthellic algae reflect); this is by far the MOST IMPORTANT FACTOR as per currently known science, NOT PAR as many think. But unfortunately this is also a very difficult parameter to measure.
- This includes exacting nanometer spikes to obtain necessary photosynthesis at varying depths of water for freshwater plants or photosynthetic corals, clams, etc. in a reef aquarium.
Reference: Nanometers in Aquarium Lighting
Although still a popular measurement, the watts per gallon is part of the lighting equation as stated above is highly inaccurate when taken by itself. Taken together, the first FIVE points are the most critical (which does include watts per gallon), but not one of these should be a sole determiner of the lights.
As an example of the inaccuracy of the watts per gallon so-called rule, please consider these comparisons for an assumed 20 gallon aquarium using High End LED Lights (GroBeam) and T8 or T12 Fluorescent lights such as the Flora Grow (by Hagen):
* 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 Flora Grow while this same 20 gallon freshwater aquarium would only require ONE 12 watt TMC GroBeam 600 LEDs, 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/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 course the differences can vary, so even this comparison only works for the described lights and tank, this is also based on the newer Cree XT-E & XP-G Power LED emitters employed by TMC (and similar proprietary emitter bins developed by Osram Olson 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 fluorescent lights when all criteria are applied (SHO as well are also superior).
Source: T2 Aquarium Lighting, Lights
Bluntly, the new generation Osram Olson & Cree Power LED emitters, coupled advanced drivers, and Pulse Width Modulations controlling, ARE THE HIGHEST OUTPUT AQUARIUM LIGHTS PER WATT CONSUMED!
See this article I wrote for more about “Pulse Width Modulation”:
Aquarium LED Lighting, PWM
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 8-12 hours per day) this can be stretched to 12 months plus.
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 blue/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).
Determining what Lighting your Aquarium will need
The type and intensity of lighting in an aquarium affects health, stress, coloration, photosynthesis, and stimulates reproduction. This applies primarily to aquarium plants, reef corals, anemones, etc. HOWEVER this can apply to fish too such as stress from too little light of the best daylight spectrums or too much light.
Some aquarium organisms come from shaded regions, like rain forest rivers, where most of the light in their day is indirect.
An example would be Discus which are often placed in brightly lit planted aquariums where no consideration for ‘shade’ is provided. In such tanks uneven lighting would be best.
This same concept applies to mushroom anemones which do not require bright high intensity lighting, so if kept with acropora corals, the Aquarium should have uneven lighting.
Choosing Aquarium Lights, Types:
Since many aquarium keepers have requested guide to sizing the light desired to their aquarium needs, I will provide a generalized “watts per gallon” at the end of three of these newer technology lights.
LED Aquarium Lights
LED Light technology has come a long way in recent years (2011 as of this update), however many are still very confused as to what a LED can or cannot do for your aquarium.
Most cheap LEDs such as the Marineland Double or Single Bright (or even those with high output emitters) do not have the correct/best PAR, Kelvin Temperature/Nanometer Range, and most importantly PUR (PUR trumps PAR and is the most important parameter, yet the most difficult to measure).
This is where LEDs had to change for these types to be a viable alternative to other popular aquarium lights.
With the development of a few advanced LED lights such as the “high end” AquaRay/AquaBeam LED Reef & Freshwater Aquarium Lights, the use of LED lights for high end applications such as reef or planted aquariums has become a reality in recent years..
With these TMC AquaRay Lights (and a few others), there is no requirement for additional/supplemental even for high light requiring planted freshwater or Reef Aquariums with SPS Coral (under 30 inches in depth).
As well an advanced LED light provides healthy high quality light for a fish only tank and uses almost no electricity when compared to traditional aquarium lighting.
Watts Per Gallon: As a generalization and this ONLY applies to high output LEDs mentioned here that utilize these technologies:
- Latest patented emitters, such by Cree since most LEDs do NOT have patent rights as well as the Osram Olson NP Blue which is the first emitter specifically designed for reef use.
- Pulse Width Modulation Technology, NOT “current reduction” technology which most LEDs utilize and wastes considerable electrical energy as heat.
- Do NOT use green, yellow, cool white, warm white emitters
- And drivers that correctly regulate voltage over each emitters, since these are NOT bulbs that can be daisy chained together, rather electronic diodes requiring very exacting voltage
*For a high light requiring planted aquarium: .6 watt per gallon.
*For an advanced Marine Reef: .8 watt per gallon
For LED light fixtures that do NOT meet the above requirements, here are the suggested watts per gallon:
*1.25 watts per gallon for the AI Sol LED
*1.25 to 1.5 watt per gallon for the EcoTech Radion
*2- 2.25 watts per gallon for Taotronics, Ocean Revive, Evergrow and similar relatively quality Chinese LEDs
*2.75-4 watts per gallon for the Marine Double Bright, Sky, Finnex, Fluval, and similar low end Chinese LEDs
T2 Aquarium Lights
(Pictured at the top of this article)
These are probably the second newest lighting development (as of writing this article update). Similar to the T5, but with a higher yet lumen per watt output in even less space.
Although not available in as many sizes and wattage outputs as the T5 (making it not always the best fit as compared to its older technology cousin), it makes up for this in its simple diversity that allows for linking multiple lights together for larger tanks or higher output.
The T2 Aquarium Fixture has another feature most T5 lights do not have; a directional lens which allows for better directional light control which equates to better focused lumens, which is especially useful for planted aquariums or small reef tanks (not as necessary for fish only tanks).
The T2 is an excellent cost saving compliment to LED lights for Basic Reef or high light planted freshwater tanks (the T2 is best “supplemented” for the highest light need tanks); while for all other tanks the T2 can be used as a stand alone low operating cost light.
Even when compared to low technology LEDs such as the Marineland Single Bright, a 13 Watt T2 actually out produces the Marineland Single Bright in useful energy (based on measured PAR, spectrum analysis, etc.)
Even a longer tank, such as a 6 foot aquarium can have 3 or 4 T2s linked together to make a superior upgrade from outdated T8 or T12 lights many freshwater fish only tanks still employ, with an increase in useful light energy and a decrease in electrical operating costs due to vastly higher efficiency.
Source: T2 Aquarium Fixtures
Watts Per Gallon: As a generalization, 1 to 1.25 watts per gallon for a planted aquarium
For Marine Reef, 1.50 to 1.75 watts of the the 6400K lights (mixed with other light types such as T5 or LED Reef Blue for the UV-A Blue light necessary for many reef inhabitants)
SHO CFL Lights
SHO Lights have been used for a few years in hospitals and Commercial Nurseries/Hydroponics operations with exceptional results for plant growth, but these SHOs are a bit newer to the Aquarium hobby.
Dollar per dollar, there is likely no better plant light, whether aquarium or terrestrial, especially when used in polished reflector to concentrate light energy.
See: SHO Aquarium, Hydroponics CFL, lighting
Watts Per Gallon: As a generalization, 2 to 2.5 watts of Daylight SHO Lights are required for planted freshwater aquariums
For Marine Reef, 2.25 to 2.75 watts of these SHO lights (possibly mixed with other light types for the UV-A blue)
Although not as high in lumens per watt output than its newer cousin, the T5 has many sizes and wattages to fit more high lighting needs aquariums than the T2, and is a popular aquarium light for many good reasons (especially for many reef tanks).
However, many aquarium lighting needs would be served as well or better with lower initial cost and operating costs with a T2 Light; sadly many aquarists (& even aquarium/fish forums) are not even familiar with the T2 and continue to push T5 lights when in many instances the T2 would be the better choice
Watts Per Gallon: As a generalization, 2 to 3 watts of Daylight T5 Lights are required for high light planted freshwater aquariums
For Marine Reef, 2.5 to 4 watts of T5 lights (mixed with actinic UV-A blue)
T8 & T12 Lights
These are the old stand-by of the aquarium industry and are still good for fish only, FOWLR marine aquariums, and low light planted aquariums.
For Reef or high light planted aquariums, these are generally a poor choice, not because they do not work, but because it takes so many of these lamps to produce the results of more modern aquarium lighting options.
Watts Per Gallon: As a generalization, 3-4 watts of Daylight T8-T12 Lights are required for planted freshwater aquariums
For Marine Reef, 4-5 watts of T8 lights (mixed with actinic UV-A blue)
TANK SET UP LIGHTING SUGGESTION EXAMPLE:
As a guide I will make a few suggestions in the following section using a 20, 60, or 100 gallon aquarium, which can then be extrapolated either up or down for larger or smaller aquariums.
Please consider the more in depth article, your personal aquarium parameters, inhabitants, budget (which is always important), when deciding what lighting systems or combinations there of to use.;
Referenced From: Aquarium Lighting Set Up Suggestions
Light (lamp) Placement:
Pendant vs. MirrorThe advantage to a pendant reflector over a mirror (depending on reflection quality) is that it will radiant downward in a slightly more magnified fashion than a mirror, however the mirror has one advantage over the pendant and that is more wide spread light distribution.
So this choice comes down more to tank arrangement of plants or corals.
What is often a bigger issue, especially with deep reef tanks (over 24 inches) is to allow as much of the blue light as possible through into your aquarium, as 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 “Daylight” in your light “mix” may be necessary for coral tanks or in some cases high light requiring plant tanks. The use of 14,000K MH in a mix with High PAR 6400K SHO lights may provide the “mix” necessary for deeper tanks.
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 >HO LED light strip may help provide this.
Here are two sellers of these aquarium light products:
SHO Lights &
AquaRay HO LED Lights
Specimen placement is just as important as light penetration since a SPS coral or Maxima Clam placed 12 inches under the the water will receive more light energy than these same specimens at 24 inches (this goes for freshwater plants too).
I recommend that corals be placed as high up in the water column as possible, this 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 sandy lagoon bottoms.
If this light is for Freshwater plants I would move the high light requiring plants directly under the lights (or even elevate them with terracing, which can look quite attractive if done well and serve a dual purpose of aesthetics and better light energy absorption).
Further Reference: Freshwater Aquarium Plant Care, Information
Another aspect of specimen placement is the type of light used.
All fluorescent lights have what is called “Re-Strike” as light is sent in every direction, then striking objects and re-striking the lamp itself, often multiple times, hence “Re-Strike”.
Unless you are using a reflector, which is recommended whenever possible such as with SHO lamps, the area of best placement is not too well defined other than right under the tube or CFL.
The problem with fluorescent lights (in particular without a good conical reflector), is depth penetration; so placement of delicate specimens need to be as close to the surface as possible, in particular with lower powered fluorescent lamps. This is not as much as issue with some HO T5 and SHO lamps.
However, as per Metal Halide or LED lights; these lights have a clearly defined cone under the lights where the Lux/PAR gets lower the further from the center of this cone of light you place your important light sensitive specimens.
So with this in mind, it is important to place high light requiring corals, plants, clams, etc as close to the center of this cone as possible, while placing less sensitive plants, soft corals, etc. further out from this cone of light.
For the full article from which much of this information in this article was used with permission from, including Lighting Types and vastly more expanded & updated lighting information:
AQUARIUM LIGHT; FACTS & INFORMATION
Copyright 2014, By Steve Allen
OTHER RELATED/SUGGESTED READING FOR AQUARIUM OR POND KEEPING:
*Aquarium or Pond UV Sterilizer Use; Level One
This is an excellent article for those who value their fish. While many persons have use so-called UV Sterilizers, what in reality were used were UV Clarifiers. This article set this difference straight and explains why spending more money for a true level one UV Sterilizer is worth the investment.
*Saltwater Aquarium Care Information
For the best in premium hot cathode 95% UVC emission UV Bulbs, I suggest these as per my many friends in the aquarium industry/hobby:
* UV Bulbs; For Tetra, Turbo Twist, more