Yes, you can keep corals, even most SPS, with PC lighting. You can also keep clams, but I've heard only crocea and derasa. I will set up a 55 in September and my parents will get me a 4x96w PC system for xmas. The 4x96 is not quite enough for some SPS and maxima clams. There are 2 6700k daylight and 2 7100k actinic tubes. I will use MH in a few years on this tank. I think 2 175w bulbs would kick butt on it.