got my second light today so I now have both sides of the screen with a light on them...still only getting the brown algae that appears on your tank glass as of now...im thinking a couple more weeks until maybe some green hair starts...I know have them on for 3.5 hours and off for 2.5 hours and so on...making it 14 hours total per day that they are on...that gives them 2 more hours then my tank lights