They are known to do so, but if I were you, I'd not expect them to do so. You would probably be better off in attempting to catch all the fish in your tank and utilizing one of the ich treatments you can find described within this board. Even if the cleaner DOES get all the ich off, the life cycle of the parasite will not be broken. The tank has to be free of fish for a period of about 2-3 days I believe to break the life cycle of the ich parasite.