Best color spectrum for coral growth?

[Gregcoyote]

Studies have shown with Acropora species that they will grow under a number of lighting combinations. At depth (most acro is found in less than 30' of seawater) the predominate frequency is blue. Closer to the surface that changes obviously. Most of (not all) these corals evolved under mostly blue light. That doesn't mean they can't absorb other frequencies, but those other frequencies can change the type and amount of algaes in the corals flesh. So acros grown under sunlight tend to grow fast but are brown in color as the sunlight has promoted extra algae growth and coloration. So it comes down to a balance between observable color and growth. I personally hate the black light look as I have never seen a glowing coral reef in the wild. I prefer a balanced full spectrum look including some UV. Some colorful corals are that way in a effort to protect against UV that can penetrate as much as 200 meters of seawater. The little bit of UV light I use seems to color up the corals better. But this is subjective so far.

http://www.whoi.edu/oceanus/feature/shedding-light-on-light-in-the-ocean


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[jeffaquarius]

The way I interpret the color absorption of Zooxanthelle posted by Mebbid is that when the subject (coral) is exposed to each color in the band one at a time, it will absorb only such an amount . Meaning each source of color will have exactly the same intensity or wattage and the graph shows how much is being absorbed by the coral. The graph does not mean that the coral must receive all those colors at the same time to have a favorable photosynthesis. As you can see, the blue color is in the highest peak which means the corals absorbs the blue much more than the other colors. You can use any color in your tank but other than blue you need more intensity or wattage to get even with what the blue can accomplish. But then, in this hobby we wanted to please our eyes and we don't want to see just blue in our tank. So we have to balance it. Again, the OPs concern is just the growth. I hope it answer his question. Think of it as in what frequency can your micro oven will cook your food.

 

[Gregcoyote]

Informative thread on another forum about this.

http://www.thereeftank.com/forums/f6/coral-and-macro-algae-spectrum-186881.html


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[mr_X]

The reason why corals seem to grow slower under just blue light is that there's not enough punch in said blue light. If your blues are strong enough, they will grow corals just as fast as any other light source. The bottom line is PUR/PAR, as stated. My answer to the OP's question is to watch your tank. Turn the lights up until you are satisfied with the growth you are receiving, without bleaching the heck out of the LPS. I have only SPS in my tank at the moment, and run my 120 watt units at 100% blue and 40% white. That's about as white as I can stand to look at it. Also bear in mind your parameters. If your parameters are off, no amount of light is going to get them growing.

 

[Maridia]

I just got into corals and my lfs gave me an SPS frag for my bday last month. His advice to me was that SPS (at least mine) required different color settings throughout the day (with an intensity at about 35-40%. I have a Kissel 360W. He said that in his experience that the white helps the corals to "grow/spread", where the blue light helps to give it/retain the healthy color. I'm about a month into it and I honestly cannot say which is better. But I adjust throughout the day with about 1-2 hrs of white light, and gradually make my way to the more blues every other hour, until I have it at the bluest for about 2 hrs. And I must say, in only the 1st month, I have noticed slight growth and good coloration.

 

[Gregcoyote]

Tropical corals get variable amounts of light as waves breakup sunlight and polarize the light. As stated several times, it is obvious when among them on the reef that blue light dominates. It is also obvious that if you want to see their true colors, reds and yellows, you have to bring an artificial light source. Our tanks are the same. The corals would do fine under just blue if the intensity was sufficient. We add the other colors to enhance our view of the coral. Since there is also blue in white light, it can also be used. But it may set off additional unwanted algae production in the coral turning it brown. Most folks want a combination and with dimming fixtures you can tune it to your preference. But the coral just cares about PUR and getting the frequencies it has evolved with.


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[jeffaquarius]

I think Greg and I are both on the same page.

 

[jeffaquarius]

Aqurium flourescent lights are designed and manufactured specifically to produce optimum PUR in mind. Take for example the Geiserman Aqua Blue or the 10000k full spectrum. Your eyes is deceiving you to see both of them are white but in reality the blue band on the spetrugraph will show you about more than 10 times stronger than the green, yellow and red. It is just to please our eyes.

 

[Gregcoyote]

The interesting part is the question does browned coral grow faster? Again, studies of acro growing in frag tanks illuminated by the sun (white light) vs more colorful coral of the same species grown under blue light of the same intensity show a difference. The brown coral lays down more skeleton, but the calcification can be less dense. Water flow also effects this. Not a simple problem to study.


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[jeffaquarius]

In shallow reef the full spectrum of the sun is available at no cost and the corals have no choice but to adapt to all the colors available for photosynthesis. It is known that corals have developed a color pigment for protection. The link I attached on the 1st page explains it all why the same specie of corals can have different colors and can be due to different factors they are exposed to like the water parameter. The brown acro in shallow reef could have developed to accept all the colors and maybe grow faster due to the amount of light it receives. Its in nature that if one is exposed to something that is considered bad it soon becomes immune to it. One example is the virus which becomes immune to anti biotic. Same thing could also be happening to ultra violet light to corals.