I am battling them in my 25 as well. Using the kalk bombing method, though in a 25, I have to be careful not to over do it and spike the tank, and that's only for the larger ones I can reach. A 25gal is sadly not even enough for a CBB short-term, and I went to get a peppermint, but only found tiny ones, that I fear some of the aipstasia would eat, or ones that appeared to actually be camel shrimp. I have too many corals to risk that.
What has seemed to have to helped, is a ground up approach, reducing feedings. There is 2 occels. clowns and a cardinal in there, and they only get what they can eat, 2 small feedings daily. And I no longer feed the corals, only the plate coral twice a week. I've also added caulerpa to the display. I did this to help with the nutrient removal. I don't have a sump, so it had to go in the display. Working so far. No longer get random aiptasia attaching to the glass.