You can really do anything you want with lighting as long as the corals still get the proper amount. In the wild there are clowdy days, rainy days, periods where the sun rarely comes out for days and other times when the reef gets blasted. If you are having an algae issue decrease it for a few hours a days for a while, but the lighting probably isnt your issue. How old are the bulbs? What type of light? How old is the tank? Filtration? See what im getting at. The algae needs nutrients to grow, meaning something else in the tank is "off" if you are seeing growth, find that and make it go away and you are golden. If you can get a list of parameters, mainly phosphate and nitrate
