I have aptasias in my tank, and got a Copperband to eat them, and b/c they are an attractive. Unfortunately, the Copperband died. It seemed really agitated, but ate well for two days, and was dead on the third. It never ate any aptasia to my knowledge. It mainly ate copepods, and picked at things on the live rock.
I have a had a hard time finding peppermint shrimp here. I have never seen a shrimp of any sort in any of our LFS
stores. I have seen Coral Banded Shrimp while diving in Ka'anapali, but they have never appealed to me, nor do they eat aptasia.