Raccoon butterfly(also eats majanos) and a copperband butterfly. Do a search on the site here and you will find lots of postings about them. Peppermint shrimp are also used but again you need to do some research. If you do go with a Racoon butterfly when he is done with the aiptasia and majanos he will start eating you zoos.etc..etc
unless your a very experienced reefer don't use a fish to get rid of the aptaisia. try kalking the large ones and improving your water quality will go a long way to controlling them.