I had a 29 gallon with a 250w 10k bulb with 2 x 55 PC atinics. I thought that combo had really nice color. At first I had a 20k bulb that was a little too blue. Also, the 20k radiums are apparently not the greatest bulbs. After a few months under the 10k, my corals and clams looked amazing. As far as the heat issue goes, I had them about 8" off the water with a fan at each side of the hood and the temperature would only get to about 82, even in the heat of summer (I used to live in Albuquerque).