Mine's been in the tank for about 4 months, he did some major damage to the hair algae early on but now it's all gone so he's eating other things. He now chomps on algea growing on the glass. if I don't clean the glass for a few days you can see little kissy marks on it from where he's taking swipes at the algae.
He was about 1.5" when I added him, right now he's about 3" long and growing fast. He continually gorges on algea on the rocks and glass, I've never seen him without a full belly. My kids named him "Chomp" because of the way he goes headfirst into the rocks to eat algea.