Here's my aipstasia story. About 6 months ago I had one pop up in my refugium (under the tank). It was growing in an awkward place to get at with bolining water, calc, etc. and since the ref. was doing a good job in rearing pods for the main tank I didn't want to put a peppermint in there. I thought I'd be safe with it down there and my main tank would be fine.
WRONG!
That one aiptasia blossumed into about 12 in the ref within a month. It was right about then that I saw one crop up in the main tank. I didn't have any biological predators of them at the time so I tried to zap it with boiling water. For the moment all seemed well. It shriveled up and didn't reappear for a few days. But, of course, it did reappear along with 2 others! Over the next several months I continued to try boiling water attacks, then boiling saltwater, and finally kalk attacks. Nothing worked. After an attack they would be gone for a few days and then come back in force. By the time there were enough that started to register stress on other corals I decided that I had to do something else. I basically shut down my refugium - took it out of circulation with the tank and shut off the lights. After a few weeks of that I removed the contents and have nothing but the live rocks remaining in separate containers. That took care of the fuge, but I still had plenty in the main tank.
My salvation came in a purchase of 5 peppermint shrimp. The very day after I put them in, I started seeing the aiptasia population start to decline. First the small ones, and now even the larger ones are completely GONE! It took them only 2 weeks to completely eliminate all of them (at least all I can see). From my experience I would have to say that they are far and away the best for controlling the pest. Kalk works ok, but only if you can reach them and get them before they dart into their holes. Boiling water only affects them temporarily and it is really hard to get the whole thing. But, those shrimp... halleleulah!