the real negative about aiptasia is that they multiply rather quickly and that they sting corals and such. Otherwise, I have seen them in FO
aquariums and not present any danger. They are kind of ugly though; all brown and such...
I would get rid of them anyway...you really wouldn't want them to get out of hand.
From what I have seen, you can get some Kalk
and a syringe and inject them with it and it will kill them...Another wild idea I have seen is, take the rock out and burn it with a bic lighter...that will kill it