I was wondering about how long I should leave my daytime lights on in my 90 gallon tank? The instructions suggested about 12 hours but that sounded a little long to me. It seems that would give way to alot of algae growth?
if you keep the exports equal to the imports than the length of time the lights are on is irrelevant to the amount of algae you could get. most people keep their lights on for 12 hrs or more, just so that they can see the tank when they get home from work.