greshham is right, the bali sea hares just tear up hair algae, we have recieved them for the last 3 weeks at the shop and i took 1 to a tank i take care of. when i put it in the tank it mosied(do sea hares mosey????) over to a crocea clam and didn't move for a while, i thought, oh great, i just put this thing in here and now its dying. well to make a long story.............EVEN LONGER! i picked up the sea hare and turned it over, it was munching some algae that was on the clam's shell, it had a piece of algae sticking out of its mouth and sucking it in like spagetti.