not sure how large your tank is, but foxface rabbitfish love the stuff. the guy I picked up my foxface from had a hair algae problem, the foxface cleaned it up in under a week on his 120g. Just be careful you don't get stung.
Though the advice on scrubbing should definitely be done first, nor do I recommend getting a fish you may not really want, just to clean up a problem.
With that said, I love my foxface and his camoflauging... him and the sailfin never leave each other's sides.