i got a 3/4 inch peppermint, havent noticed him eating any aiptasia but thats prolly cuz i been killin the ones i see with hot water, hes probably eating the hidden stuff though....
I kept a few peppermint shrimp in my 38 gal...I have lots of different polyps, but I never noticed any problems with them and they did seem to curb my aptasia issues, which are few and far between now!