My experience with aiptasia is very limited. I've only had 2 individuals in my tanks, one was on a small piece of rock that I simply removed and scraped off. (Then scrubbed with a toothbrush and rinsed under tap water). The other was on a larger rock but as luck would have it (or rather the kind of luck I have!) the individual was in the midst of some majano anemones that eventually stung it to death. Of course, I still had to remove the majanos, but that's another story....
Anyway, I've heard that peppermint shrimp can work. Also some butterflyfish. If you decide that you want to get something to eat it, you must realise that there is no guarantee that any of them will work!
Good luck and let there be no survivors!!