Right now I am running the Current Orbit Series 36" 1x150w HQI, 2 96w actinics. I have the original 10k bulb, I bought the current 14k bulb and I am currently running a 20k bulb on my tank. The problem is that with a 10k bulb the corals in your tank will explode! I had Xenia in my tank and it went rediculous and spread so rapidly I could hardly control it as 10,000K is closest to actual sunlight which is about 6,500k. As you go more and more in to the blue spectrum the photosynthesis slows down more and more.