I think some parameter is missing in all the forum and thread discussion on light. They keep saying how many k per gallon, but never incorporate how many hours they keep the lights on.... and the number of hour plays a crutial part in the final result. So, I would suggest we use a matrik of ?W/?G@?H, where W refer to watt, G refer to gallon and H refer to number of hour they are on. For example, 4W/G@10H. That's will help new hobbist like me to understand the lighting requirement.