6700K PC too green in a reef tank? 10,000K better?

[Rob]

Experimenting with my new AH Supply PC do-it-yourself kit... very happy so far, but I've got lots of questions.

This is a three * 96 watt kit on a 90 gallon reef. Bulbs are one Actinic, one 10,000K, one 6700K. The actinic turns on early in the morning and turns off late in the evening. The 10,000K turns on 90 minutes after the actinic, and turns off 90 minutes before. The 6700K turns on for about three hours in mid-day.

First, I'm a bit disappointed in the 6700K... it seems to give the tank a greenish hue that I associate with freshwater tanks, rather than the cool deep-water blue that I associate with reef tanks. But my corals and fish are the ones who really have to live with it! Thoughts?

Feedback on the time-cycle and the setup in general?

Thanks!

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Cheers,
Rob
New York City

[Bruce]

Rob,

Kelvin temperature of a bulb is primarily an asthetic choice. People prefer all types of color temps, ranging from the "pee yellow" 4000k bulb, to the vivid blue of the 20,000k bulb. There is however, a negative relationship between color temperature and photosynthetic radiation (PAR). As you increase the kelvin temperature, the PAR decreases. You are left with a trade off: The blue that YOU want, and the PAR that your corals want.

I strive to mimic nature as closely as I can in my tanks. Sunlight, in the tropics, has a kelvin temp between 5500k to 6500k. For this reason, I use 6500K 250 watt Iwasaki's on my tank(s).

So, what should you use? Use which bulbs you feel gives your tank the best look. You and your corals may disagree on which the best light is, but you can probably reach a happy medium by experimenting with the different PC comibinations. Good luck!