6 hours. I lowered it when I flooded. I can lower the actual light intensity if that would help though. Its about 5 feet away from a west facing window. The back of the tank is frosted, and there are woods behind it. It gets hit some in the morning, but not much at all. Should I put a peice of cardboard on the back to block all extra light? I can cycle the tank whenever I want... I have a ton of extra biomedia. But I don't want to put it in because it will just die off without an ammonia source. I was going to wait and just put it in when I put the fish in. I will order some spectracide stump remover aka KNO3.