I found some stuff at Wal-Mart... I can't remember what it's called, but it works wonders! It's in a white bottle with a yellow lid, and it's meant to both get rid of and prevent algea. I was nervous about it at first, but it did not harm my fish, and the algea was gone within a week. I think it's simply called "Algea Destroyer" but I'm not positive on that.