LEDs For The Reef Tank



Back in 2008 the discussion was can LEDs Grow Corals? Its now overly obvious that LEDs are the primary choice in Coral Lighting. The question that still exists is what is best? This article is based on the research of many and the practicable application in our own Coral Reefs.

Most corals available to reef hobbyists are harvested between 2 and 20 meters. This wide range of depth compounded by the lighting or lack there of provided by distributors and retailers of coral necessitates proper and diligent acclimation by the hobbyist. Proper acclimation of coral to a new environment is not what this article is about. We mention it front and center only because the only complaint we received about our LEDs is they are too bright browning out or bleaching my Coral. Of course when you upgrade your lights from Power Compacts or T5s to a 400 watt 10K XM you will have the same complaint. LEDs are also brighter than advertised, with that said the following represents our beliefs and the research of many. In our personal Reef Aquariums we have seen better growth with more rather than less light. If not for LEDs we would be recommending 400 watt MH or 8 T5 fixtures.

A corals spectral needs are determined by the depth range in which it grows. The same species of coral grown at different depths will often look different to the human eye. This by its self is a confusing statement but mother nature is wonderful. Coral are highly adaptable, infact more adaptable than one would think. Coral of the same species in the shallow reef increase certain pigments to limit the light their zooanthellea algae receive. At deeper depths Coral use certain pigments to enhance the available light. In both cases corals adjust their symbiotic zooanthellea algae to ensure proper nutrient levels and in the case of too much light Coral will expel its symbiotic zooanthellea algae to avoid oxygen toxicity.

Coral can and do adapt to a change in light intensity and Spectrum. We like to use the term Able To Use when referring to the grow spectrum. This is between 400-500nm. Based on intensity, spectrum and cost, we have found the Cree XT-E Royal Blue the best grow light for the money. At 450nm this straddles the center of the greatest photosynthetic efficiency range. This opinion based on our practicable experience growing Corals. We will address this throughout this article.



LED selection should reflect the lighting conditions in which most corals grow. Then once the grow is covered one can try different combinations on what looks best to the human eye. This is the art of Reef LED Lighting. There are many recipes on the reef forums. Some are repeatable with merit others are simply ones own opinion based on their limited experience and latest trend. One thing that a lot of hobbyist fail to recognize is the fact that most Coral in their natural environment do not receive a full spectrum dose of light. They receive very little past 525nm. With this they have adapted to primarily use the 400-500nm range.

Sanjay Joshis research with MH Lighting has been extremely influential in our development and application of LEDs as a replacement. Here is a pic of his spectral analysis of different MH Bulbs.

Ssanjay MH Test

The Spectrum of the MH Bulbs depicted are perfectly suited for the reef aquarium. The main question is which looks better and which grows better. Much of this is personal opinion.

Our mission is not to re invent the wheel but to offer a better option. We are aware that each bulb has a dominant 450nm spike. This is the base for growth. On a side note we have grown frags only using the 450nm Royal Blue. That said the 450nm is the foundation of our recipe. The Cree XT-E Royal Blue has a published spectrum of 450-465nm. We have found that bins closer to 450nm offer a much better colour pop and the difference between looks is noticeable with the Bin D36 offering a closer Actinic look and the Bin D57 offering more of a Blue look with less colour pop.

We prefer Cree LEDs as they’re industry leading in efficiency, longevity and are less likely to be counterfeited. They also Bin their LEDs and reputable suppliers stamp the specific Bins on the back of the LEDs Star. By binning their LEDs we can choose from 28 different Cool White LEDs and numerous Royal Blues. Below is a picture of our tank with two different bins of cool white. The left cool white is the Bin we offer as our Premium the cool white on the right is the more common warmer Bin. There are a lot of companies who use the Cree Cool White and Royal Blue as the base but without proper use of specific bins one cannot guarantee optimal looks. If fact one my wind up with a slightly yellow look needing more Blue or Royal Blue to compensate.


Here is the actual Binning Chart of the Cree X Series LEDs

Cree XP-G Series Colour Chart

The Cree XT-E Cool White (Blue Line) is a full spectrum LED with the exception of the Red.


If you want to recreate the natural light found shallow tidal pools all you have to do is add a few Red LEDs or a few Warm White (Red Line) LEDs. The exact spectrum of Cree LEDs varies slightly with the Bin. By choosing the correct Bin one can easily replicate the look of any MH or T5 light. We feel we have found the perfect mix in our Phoenix DIY Kits and our Sirius XTC. These focus on the Binned XT-E Royal Blue which provides the growth and awesome colour pop and a special Mix of Binned Cool White and Blue LEDs to simulate the look of a 20K Radium with the whites dimmed down or a 12K Ushio with the Whites turned up.

We chose to add the Red Spectrum for looks This spectrum is blocked quickly and nor is it readily available in the natural reef. The 660nm or Red can be used for photosynthesis but we found the 420-450nm a better grow spectrum for corals. There is also some research available that suggests that too much of the Red Spectrum in a reef tank may promote nuisance algae. Below is a chart depicting the actual spectrum available at different depths.

PhotoPenetrationPigmentsThere is a lot of online debate on which LED mix is best. Some times it is a s trivial as the question “who is hotter, Ginger or Mary Ann?”. The ultimate looks of ones Reef Tank can be easily tweaked. Once the foundation of LEDs are in place. All one has to do is add a few LEDs to highlight the desired pigments in Coral. Below is a chart from Dan Kelley that depicts the different pigments in Coral and how they respond to different spectrums of light. Our Sirius XTC uses 7 RGB clusters. Each Chanel is controlled separately which results in over 68 trillion color variations. We like to use the 410-470nm spectrum as our primary grow and then adjust the

DSC_0495_zps7a399bb1 rgb-color-mixing_zps1692b09c


We found that our Binned Mix of LEDs hits most of these pigments giving a very nice look. On our personal SPS and Mixed aquariums I’ve experimented with adding some Reds and Greens and can honestly say a little really adds to the look. Our Royal Blue are 445-455nm and given their brightness really do cause the coral colour to pop. Adding some 410-420 Hyper Violet / UV do bring out some extra colours. These LEDs are not nearly as bright as the Cree XT-E but do offer a desired and naturally available spectrum. Given the fact that Coral have an “able to use spectrum range” and that these LEDs are not nearly as bright as the XT-E, I do not consider them a Primary grow LEDs or necessary. A lot of factory fixtures have a couple of these LEDs but this token amount is only for marketing. We’ve found that you need at least 6 over and area of 24″x 24″ driven at 700mA to make a difference. This is why we have 6 Semi P2NU In our Sirius XTC. These with a hint of Deep red really add to the looks.

Color Balancing


With a Multi Channel Fixture one can tun the LEDs for optimal looks and growth. Below are the Spectral Charts of our Sirius XTC. Our Phoenix DIY Kits will offer similar results but also offer more customization.
XTC Full SpectrumSirius XTC w all 9 Channels at 100% Appx 10K
XTC Factoryl SpectrumSirius XTC w Reduced Factory Settings, Appx 15K
We would like to personally thank Sanjay Joshi and his research which led us to finding the best, most cost effective LED alternative to MH Lights. His spectral analysis of popular MH Bulbs led us to our opinions and success.


How many LEDs do I need

The  following recommendations are based on our personal experience and feedback from numerous customers. We chose to compare LED builds to the rough equivalent of Metal Halide Bulbs. There are a lot of variations that will affect PAR like optics, type of LED or type of Metal Halide Bulb. A 250 watt 10XM will have more PAR than a 250 watt Radium. A 60 LED Build with Optics will more PAR but less spread than the same 60 LED Build without Optics. There are hundreds of different ways to do LEDs right and thousands of ways to do them wrong. Our recommendations will get you started. The wonderful thing about a DIY LED build is you can approach it with a modular concept with the intention of adding to it later.

Our minimum recommendation is the following: use the 175 watt MH equivalent for Softies and a 250 watt MH equivalent for LPS.

We prefer more light on a natural schedule. 400 watt MH for SPS and Clams is a minimum. Along with Sanjay Joshi, Sven Fossa and Alf Nilsen authors of the Modern Coral Reef Aquarium have been influential to the way we set up our personal reef tanks. Here is a graph of the natural light on the reef from their first book.

Daytime LUX


Sanjay Joshi has recommended a minimum of 100 PAR on the sand bed with higher light corals placed higher up in the tank. We took this and with the above chart have had great results with 200 PAR during peak hours on the sand bed. Our LED Drivers are dimmable, so they can with the proper PWM Controller simulate the natural intensity depicted in the above graph. For reference on a sunny July day up here in the Peoples Democratic Republic of Cook County Illinois measured LUX at 1PM was 111,000 and PAR was 1915. Cook County rests on a latitude of N41.45. The declination of the Sun is about 20 degrees to the south and offers much more intensity over the Coral Reef. A 400 watt MH Radium gave us 424 PAR at 24″ and our Sirius XTC Fixture rated at just over 600 PAR at 24″ in free air.

We as hobbyist and coral growers do best when we simulate the natural light at the depths our corals are most accustom to. This statement can be ambiguous as the same species and sub species of coral are found at varying depths with an peak intensity at the lower depths being a fraction of the surface. That said here is our recommendation based on our practicable experience growing coral frags. The number of LEDs are Cree XT-E with Carclo Optics driven at 700mA.

For 20″-24″ Deep Tanks

175 Watt MH 250 Watt MH 400 Watt MH
12″ Heatsink will light Approximately 24 x 18 18 LEDs 24 LEDs 36 LEDs
18″ Heatsink will light Approximately 30 x 24 24 LEDs 36 LEDs 45 LEDs
24″ Heatsink will light Approximately 36 x 24 30 LEDs 45 LEDs 60 LEDS


For 30″ Deep Tanks

175 Watt MH 250 Watt MH 400 Watt MH
12″ Heatsink will light Approximately 24x 18 18-24 LEDs 24-36 LEDs 36-42 LEDs
18″ Heatsink will light Approximately 30 x 24 24-36 LEDs 36-48 LEDs 45-60 LEDs
24″ Heatsink will light Approximately 36 x 24 30-42 LEDs 48-60 LEDs 60-72 LEDS

Remember this table is for rough planning. 42 LEDs on a 12″ heatsink will produce a lot of heat and require an efficient cooling fan. Thermal management is key. If your heatsink is too hot to hold tight its too hot. On one of our 72 LED fixtures we have a single 200mm NZXT fan that works great to keep it cool. For a general recommendation our favorite combination is 24 XT-E Royal Blue 15 XT-E Cool White and 6 XP-E Blue. Using our Binned LEDs will result in an awesome look. Using dimmable the drivers from our Phoenix Kits and an APEX Controller the XT-E Cool White are dim in the morning and evening for a very pleasant 20K colour temp. Over a period of several hours the Cool White ramp up to 100% and give a colour temp between 12-15K. You can also have the Cool Whites dim slightly in a random fashion on multiple fixtures to simulate cloud movement. Both Bill and Rick have this combination on their personal tanks and is the equivalent to a 400 Watt MH.


Our Tanks may be square typically but that does not mean you have to design it to only work with squares!

Angle your heatsinks with our hanging kits to aim the most of the light onto your rockwork and corals.




Rotate your heatsinks to avoid overflows to make the most of your lights.






This tank is perfect for our base recommendation: 36 XP-E Royal Blue 12 XP-E Cool White and 12 XP-G Cool White High Noon kit. The basic equivalent to a 400 Watt MH

Single 24″ x 8.46 heatsink

Two 12″ x 8.46 heatsinks


Three 12″x8.460″ Heatsinks


Two 18″ x 8.46″ Heatsinks


Note that the spread appears to be quite large. In reality over 50% of the light is concentrated in the inner half of the cone.

If you slightly angle the fixture towards the center and back, you would be maximizing efficiency and allowing less light to hit the glass.




now the fixtures are 7″ above the water so we put 80 Degree Optics to get more spread. No optics give you even more spread.

Note: Most of the light is in the inner half of the cone.



For a heavy based SPS tank Three Cree 48 XP-E Kits would work great. High Noon Kit option would work better.




In this example spread the three 48 LED kits on four heatsinks to maximize thermal management and coverage.



All images and content provided is intellectual property owned by ReefLEDLights, Captive Reef Ecosystems and may not be redistributed without authorization.

2 thoughts on “LEDs For The Reef Tank

  1. I have a 36″ bow front Fluval aquarium that I am looking for new L.E.D. light system for. I have soft corals now but would like to get some hard corals as well. I also have a couple of small fish. I would like the coral’s colours to pop. What combination would you recommend? Thanks Cathy

    1. Cathy, corals pop best under blueish light. But it’s all your preference. You can look at a tank you like and ask their color combination. I prefer 2 blue LEDs for every cool white led.

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