I too struggled with aiptasia and just the right choice to eliminate them. I used Aiptasia X and it worked great but there were always new aiptasia popping up somewhere else, it was a daunting task. I had tried 1 peppermint shrimp but didn't have much luck. I checked into file fish but they too are a hit or miss plus they can pick on corals. I finally found a deal online for peppermint shrimp (locally they were $10 each) for $3 each so in frustration with my aiptasia I ordered a dozen. Crazy I know.....but it worked. They eliminated every aiptasia that I can see. Now that the aiptasia are gone they dance around all over my tank darting in and out of rocks.
Point being, as others have said, although peppermint shrimp can be a hit or miss when it comes to aiptasia removal, add several and hopefully like me you'll have them having the herd mentality and some will definitely do the job.