Well of course nothing works in a vacuum. Our tanks have too many variables for anyone 'really' to tell you straight out what caused BGA in 'your' tank. Point I was making about the lighting is that it might have been fine for a while, but over time as organics built up the light was too much. The one thing ALL tanks have is organic decay and how each tank deals with it. Higher light will usually result in worse algae situations if the organic decay can't be kept in check. Even when you can a tank well over time the decay builds up.