if you picked up some new zoas recently, they probably hitchhiked.... One way you can get rid of them is picking them off with tweezers. Another way is by dipping them in a FW+ iodine solution. There's a product out there called Lugols, I haven't used personally, is also suppose to do the trick.
I forgot who, but someone one on the forum picked up a wrasse to take care of their pest problem. I don't recall how that went.
What you have to worry about are eggs. I don't know of any solutions for that yet...
I hope that helps. Good luck
-Jay
edit* the link is a good source of info. I'm still skeptical about dipping the zoos in hot water. Let me know it goes.