had a problem in this in my 60 gallon reef, before switching to the 125. it was mainly phospates (used to use treated tap water). once i put in the RO filter, phosphates must have decreased, because no more hair algae and none in the 125 now. you can use phospate sponge to lower them now, but they will just creep back up on you if you don't fix the original problem. I was also feeding too much.