color temp and coral growth

[imcosmokramer]

Can someone send explain (or put a link) the effect of color temperature on coral growth. More specifically, I have heard that a 10k bulb will promote more growth than a 20k, where as the 20k influences color. However, does this mean that you can use the 10k for the growth period and then switch to 20k and the coral will acquire more color? Or does it simply mean that the coral "looks" more colorful under 20k? or, will the coral ACTUALLY be more colorful if grown under 14, 15, or 20k vs 10k?

Hope this makes sense to someone.

[abulgin]

Here's a start: http://www.wetwebmedia.com/marlgtganthony.htm

As color increases, you get a corresponding decrease in useful spectra. The higher the temperature, the more blue the light. Photosynthetic corals grow "best" under 6,500K lights, but that is way too yellow for most hobbyists' taste.

Really, we need to know what type of lights you're using, as I think I would have different recommendations for HO T5s than I would for metal halids.

[imcosmokramer]

I currently use 2x250w 10k plus 4x54w actinics, however, my questions however were meant to be more general.

If for example, you wish to set up a frag tank for sps. Would you use 10ks to induce growth? or 20ks? The real question is, do the 20k bulbs MAKE the coral more colorful, or just LOOK more colorful?

[abulgin]

The 20,000K bulbs just make them look more colorful. The deep blue in the higher temperature bulbs cause corals, especially green corals, to fluoresce. You will actually get very little, or at least very slow, growth with 20,000K bulbs.

For a frag tank--I presume a tank that isn't really a "display" but is used to propogate coral frags so you can sell them, add them to your display, etc.--you actually would be best served by 6,500K MH bulbs.

[Toddrtrex]

I am getting fairly decent growth with my 20K bulbs. ( granted I am using 2*250 watt over a 58 )

I have also notice that my Tri-color has more blue in it now, and not just because of the blue cast -- it is noticeable even when I take a picture with a flash, and when I do that when the lights are off.

[abulgin]

I'm not saying you won't get any growth under 20,000K bulbs, but I think you will find, if you search sources, etc., that most experts agree (including A. Calfo) that photosynthetic corals grow best under bulbs having temperatures that approximate the sun. 20,000K bulbs don't approximate the sun.

[Toddrtrex]

I am not saying that one would get better growth from a 20 K compared to a 6500K bulb. Just saying that I still get good growth from mine. And for me, color is more important then growth.

[abulgin]

I totally understand. But for someone who's looking for a light over a frag tank, I think growth is more important thatn color.

[Toddrtrex]

Originally posted by abulgin
I totally understand. But for someone who's looking for a light over a frag tank, I think growth is more important thatn color.

I agree and disagree.

Would think that for a frag tank a balance would have to be found. I know that I wouldn't care how big the frag is if the color was awful. But, I do understand your point about wanting growth in a frag tank.

[imcosmokramer]

well, to bring back some of the original point. Could you use 6500/10k for growth, then switch to 20k and it will add color?

[Toddrtrex]

Yes you could do that.

How big is the frag tank ? I know that others have run a 10 K and a 20K bulb next to each other to get the best of both.

[styndall]

From Chris Jury's Renaming Our Corals, located at:

http://www.reefkeeping.com/issues/2006-03/cj/index.php

Beyond this, complex environmental and physical factors interact in ways that are still not understood to make corals either produce or not produce colorful pigments. Light is certainly a critical factor for the production of at least some coral pigments (Dove et al., 1995; Dove et al., 2001; Salih et al., 2000), while others do not seem to be induced by light intensity at all (Mazel et al., 2003). Both an additive (like internal reflectors) and a subtractive (like Venetian blinds) role has been assigned to certain coral pigments (Dove et al., 1995; Dove et al., 2001; Kawaguti, 1969; Salih et al., 2000; Schlicter et al., 1986). Mazel et al. (2003) argue that these pigments likely do not have a photoprotective role as has been suggested recently by Dove et al. (2001) and Salih et al. (2000). Personally, I find that the case has been well made that at least some coral pigments (certain GFP-like proteins-the "pocilloporins" of old) likely are playing a photoprotective role in certain corals (particularly in pocilloporids and acroporids) but also that certain other pigments (exemplified by GFP, green fluorescing protein) are not involved in this process. I think that, to an extent, each set of authors may have slightly overstated their positions. This leaves all the other coral pigments (and there are many) with unknown functions or cues inducing their production. Especially interesting are the pigments produced by azooxanthellate hard and soft corals. What purpose or function might these pigments have? While hypotheses have been offered, no consensus has been reached. The functions and the factors that induce the production of these and many other pigments in zooxanthellate corals are currently unknown, but in many cases light probably is not a factor (at least not directly).

Coloration is a lot more complicated than the color temperature of your lights.

[imcosmokramer]

I was not suggesting that coloration was a direct outcome of color temperature, but was trying to identify how much of a factor color temp is.