The problem with Berghia is they only eat Aiptasia (and I can't remeber if they eat the larger ones or not), but once they have eaten all the Aiptasia, unless you are willing to set up a jar or small tank for them with plenty of Aiptasia in it, they will starve to death. They are also very hard to come by, you have to get them online. I've never seen a LFS carry any. I agree with Truckin, I tried the Peppermint shirmp and they didn't seem to make a dent in them.
Stephen