I just made a mess of my tank with aiptasia x. I prefer giving them a lethal injection of vinegar. If they're small, and you have a lot, a copperband butterfly does wonders. They will first go after any small feather dusters and tube worms, but will then wipe out the small aiptasia. Just make sure you have a well established tank and it's a healthy fish, eating frozen food first, to be sure it does ok. I bought one the other day at JKS and it wouldn't eat frozen food at the store...but did show a lot of interest in it. I got it home and within a day it was eating frozen mysis.