Well, if you can very carefully pull them off with forceps or something like that without breaking them, pull them off, remove them from the aquarium, put them in a little cup of water and bleach and dump. Best to nip them now. A possible long term solution are emerald mithrax crabs (fairly common in LFS), which have been known to eat them. The problem is that behavior varies between individuals (some just won't eat it) and I've heard that some don't consider them completely reef-safe, they may be a slight threat to inverts or very small fish if you get an aggressive one. I would try to manually remove them now, if you can pull out the rock they're on, that's definitely worth a shot.