I brought an aiptasia home as a hitch hiker on a coral fragment I bought from my local LFS, and they started multiplying fast as well. I went out and baught a peppermint shrimp and I was very pleased when it destroyed all four of them within the first 24 hours after being introduced to my tank!! I def. recommend getting a peppermint shrimp or two, dependign on the size of your tank.
Good luck!