Algae outbreaks are common in a new tank and also if you use water that is not pristine enough. (R/O is highly recommended). It can take weeks or months to eliminate the problem. Use R/O water (if you're not already) and get a alot of snails (preferably turbo and/or cerith snails). I believe it's one snail per 2 gals. but you can check under reef packages or inverts at SFW for the best number. Good Luck! :happyfish