Lots of good advice from previous posters. I second the notion that biological control is better than most other methods when trying to deal with an Aiptasia outbreak. I have had the sad experience of using a chemical method to kill the single Aiptasia I could see and finding a month later that I had an entire tank of them. Others may have had good results, but unless you only have a few and do the eradication PERFECTLY, trouble is likely to follow.
I have had great success with a matted file fish, Klein's butterfly and occasional success with peppermint shrimp, which are hit or miss in my experience. I think that once you have Aiptasia in the tank, they are likely to always be around at a low level, particularly if you have rocks with deep crevices like the Pukani that I have. The filefish and butterfly control those that are accessible in my 150, but I can see some Aiptasia tentacles down in the crevices. I may try a Copper banded butterfly or Berghia to get these, but so far they are too few to worry about.
Good luck,
Bruce