Other LED wavelengths for coral lighting

[Crit21]

I try to keep up to date on reef lighting. A combination of white, blue and royal blue LEDs have been the norm so far. I've had great success with them over hard and soft corals. Hobbyists and manufacturers are now experimenting with LEDs of other wavelengths.

I've been researching high power LEDs recently, and have come close to finding a combination of shorter wavelength LEDs that somewhat match the coral photosynthetic action spectrum. I'm still looking for a 1W or 3W LED centered around 430nm to fill the last spectral gap. Between violet and green, I would only need 6 colors to duplicate the coral photosynthetic action spectrum. I'm on the fence as to whether I'd use the 410nm violet.

The coral photosynthetic action spectrum is only an indication of the amount of photosynthetic response to each wavelength, and is not an indication of the visual appearance of corals illuminated by them.

I still have a couple of unanswered questions though:
- Compared to using just blue and royal blue LEDs, what would the overall appearance of corals be if equal numbers of the 6 different LEDs were used?
- Compared to a combination of white, blue and royal blue LEDs, what would the overall appearance of corals be if equal numbers of the 6 different LEDs were used in addition to white?
- What will be the difference in coral growth and health if I use the 6 colors instead of just one or two blues?
- What will the effect be on pigmentation?
- What will the effect be on phosphorescence? (I think I remember articles that address this)
- What is the best percentage of each color for growth? For pigmentation?

 

[Crit21]

So what wavelengths stimulate coral pigments to fluoresce? In Part 1 of a multi-part article in Advanced Aquarist (http://www.advancedaquarist.com/2006/9/aafeature), 214 corals were tested for fluorescence (See Table 1 in the article).

Only 7 fluorescent pigments were excited by wavelengths below 400 nanometers (the UV region), and two of those were close enough to 400nm to be excited by LEDs with peaks just above 400nm. 47 were excited by wavelengths in the 400-449 (violet) range, 29 in the 450-499 (blue) range, 22 in the 500-549 (green) range, and 15 in the 550-599 (yellow) range.

Does this mean that I should be using LEDs that emit wavelengths from violet through yellow to get the maximum display of fluorescent emissions? Assuming any white LEDs are turned off, would the resulting light from these violet-yellow LEDs appear to be blue-green?

I don't want to have a series of green and yellow LEDs just to be able to see my corals fluoresce. The priority is coral health and growth. I think the idea of using green and yellow LEDs just for fluorescence is not a good one.

 

[projectx]

In what ratio would you use all 6 of the colors? or would it be 1:1 ?

 

[Crit21]

I have the same question. Even if the numbers were different, it would probably require separate dimmable circuits to be able to adjust the intensity of each color independently to get whatever effect I'd want or need.

 

[Crit21]

A balance must be struck with lighting intensity too. "Increasing light intensity will cause the reduction in zooxanthellae abundance and hence colour pigments will become more apparent, however under light intensities that exceed a corals saturation point metabolic activity by the coral will decrease, colours will pale and in extreme cases the coral will bleach." (http://reefworks.co.uk/articles/obtaining-the-best-colours-from-your-corals/)

I've come to understand that the LEDs at the left end of the spectral chart cause a huge increase in photosynthetic response. They can easily cause corals to reach the saturation point, where photosynthesis stops and photoinhibition begins. In other words, it's very easy to "overdrive" the corals and zooxanthellae with too many LEDs in the more energetic (blue/violet) end of the spectrum. Many of us noticed coral bleaching and zoanthid shrinkage shortly after turning on our first blue-intense LEDs.

What this is telling me is that I need to be careful that I don't use too many of the blue/violet LEDs or I risk killing my corals.

 

[Crit21]

In an earlier post I said that I determined that 20 watts of LEDs per square foot of tank footprint were a good goal. This was based on the analysis of a commercially available LED. I'll probably be going a bit higher, with the thought that I can start with them dimmed to 50% at first, then slowly dial them up over weeks or months until I get the desired effects in growth and coloration.

 

[Crit21]

So now I've got the number of watts per square foot, which tells me how many total LEDs are required, but I'm still left with the question of how many non-blue/royal blue LEDs are best for growth, aesthetics and fluorescence. I don't see posts on any forums that discuss the issue specifically, except that adding a few violet or teal LEDs is "really cool". I may have to figure this out through trial and error. Sounds expensive.

 

[lpsouth1978@msn.com]

I think that a lot of your questions can only be answered through trial and error, however I can give you my experience with the use of "non-traditional" spectral pairings. First a background on the tank that this light is currently over. The tank is a 34 gallon Current Solana all-in-one tank, 20x20x20. It is primarily an SPS setup with some acans, mushrooms, and paly's. It has been up and running for almost 2 years and had a 400W 14K HQI bulb run at about 280W using a Galaxy dimmable electronic ballast. Under this light things did well and everything was quite happy.

About 8 months ago I built an LED fixture for this tank. The fixture measures 16x16. I decided to use 24-cool white, 12-neutral white, 6-blue, 24-royal blue, 3-405nm UV, 3-red, and 4-RB moonlights. All of the LED's are Bridgelux 3W using 80 degree optics. The red, uv, and moonlights use no optics. I used buckpucks for the drivers and put each color on its own dimmer so that I can set the color the way that looks best.

I have also used just RB and Cool White on other builds, but the corals seem to do better with variation in spectrum. I am no expert or scientist, but I don't think the results lie. The colors of all of the corals in the tank is fantastic! My almost bleached (8 months ago) Ponape Birdsnest has an incredible pink color, with green towards the base, and has grown from the size of a softball to almost the size of a football. My red acans which had turned orange under the halide, are red again. While I cannot conclusively say that the spectrum has made all of the difference, IMO it has done wonders! My other two builds (using only blue and white) simply have not had the same results.

I can also say that I am glad that I did not use equal numbers of each LED. If you are looking at any red or green, be VERY careful, even with just 3 red, I have them turned down to about 15-20%. Any more and it is simply too red. Also, if you use any UV, be cautious, they do not put out much visible light, but there are a lot of reports of frying corals by using too much UV.

You are welcome to come look at my build anytime.

 

[cdrewferd]

My build has the following:

18 - Royal Blue, 455nm
12 - Neutral White, 4500-5000k
6 - True Violet, 420nm
4 - Deep Red, 660nm
4 - Turquoise, 495nm

This is over a 29 gallon BioCube. Only been on for a month so I can't say much about growth, but color is outstanding. Let me know if you'd like to come check mine out. I'm in Westminster.


Drew

Sent from my iPhone using Tapatalk

 

[Crit21]

Thanks for the invitation. I'm in Colorado Springs, so it'll probably be a while before I get up that way, but I'll definitely contact you then. Until then, maybe you have pics to share?

May I ask why you chose red? Since most corals are taken from deep water, they don't benefit from light from the longer wavelengths.

 

[lpsouth1978@msn.com]

I chose red initially only because it was a different wavelength than is typically used. That being said, once they were working I found that I really like the colors of the corals with a little red. It may not be a spectrum that they need to thrive, but it has not harmed them in any way and , at least aestheticaly, they look better IMO. Here is a link to my build thread which has a few pictures with some different lights, including my build with and without the reds turned on.

http://www.marinecolorado.org/forums/showthread.php?9012-My-latest-DIY-LED-build