[kevinpo]

Coral coloration is a very complex thing and I will not try to explain in detail why or how, only a few tips to achieve the coloration you want.

The first thing to consider is water quality. Most photosynthetic corals we keep like water low in nutrients and phosphates, but high in calcium, alkalinity, and good water movement. Lighting is also important more or less so depending on what type of coral you intend to keep. Your choice in lighting will also influence they way a coral appears to you. For example a blue coral appears much different under a 10,000K bulb than under a 20,000K or 6,500K bulb.

When shopping for a coral be sure to ask a few questions like, "How long have you had the coral? What type of lighting is it under? Was it captive raised?” These simple questions can go a long way in helping you to maintain the coloration of the coral as it first appeared. Be sure to note the depth and position of the coral in the tank it came from.

The question I often get is "I bought a coral from you and it was (insert a certain color here) and now it is (insert another color here). If the water quality is good then the color shift most often is the result of a change in lighting intensity. This can be adjusted easily by moving a coral up or down. Moving a coral to one side can also change the light intensity if you are using halides (this is not true for fluorescents).

Soft, LPS, and green colored SPS corals are the easiest to maintain color but even they can have a pretty wide variation in their coloration. For example I have a Acropora yongei that ranges from a dark green to almost yellow in the same tank just placed at different heights. Stylophora pistillata is another coral that range from light pink to dark purple depending on light intensity.

Generally speaking corals will lighten in higher light and darken in lower light. Health and growth rates are about the same once the coral adjusts to its light level regardless of whether it has lightened or darkened.

So if you don’t like the color of your coral try changing the light intensity it receives. Be sure to give the coral time to adjust. Also you can burn your coral if you increase the light intensity too quickly. I move a coral only about 6" upwards at a time and then wait a couple of weeks to see the final color. You cannot hurt the coral by lowering the light quickly.

Regards,
Kevin

[scubadude]

Kevin
Whats your opinion on Iodine and its general effect on coral coloration? I have heard from others that it affects their coloration.

[kevinpo]

Hi Rocky,
I wrote an answer to your question last night but I don't see it here now
Anyway over the years I have tested for total iodine/iodide and found the levels to match or exceed NSW in my tanks. My corals seem to have OK color, to me, for the last 4-8 years. I have also sold many of my corals to people with a very wide variety of tank conditions and lighting (both spectrum and intensity) and they seem to hold their color pretty much the same as in my tank with some slight variation. So IME/IMO it is not a crucial additive for coral coloration

Regards,
Kevin

[Reefland]

Alkalinity??

[kevinpo]

Alkalinity has mostly to do with growth rather than color. I have let the alkalinity lower to 1.8 meq/L and the only difference I have noticed is the growth rate slows way down. I have seen corals bleach, RTN, and STN from running the alkalinity too high or suddenly raising it to high levels. NSW runs about 2.57 meq/L but I run my tanks slightly higher. In my aquarium log I think the average is about 2.97 meq/L.

Regards,
Kevin