larger peppermints have a better chance of eating them. get 2-3 to increase your odds, and make sure you drip acclimate for 3 hours or so , to keep their health optimal. i did this, and they destroyed all of my aip.
give them a little time too. sometimes when you start trying to squirt the aip, it goes crazy and starts multplying like mad. natural predation is a great method, and wont mess with your calcium / alk / pH numbers.