Sorry about your copperband butterflyfish. I have never owned one ,but I have read the trick to them is to get them to aclimate and eat . It seems reasonable that a well fed and adjusted butterfly would be motivated to eat aiptasia, after fasting, but aclimate and fatten him up a little first. Once "trained" the word is they are aiptasia eating machines...and then some small polyps, tubeworms,zenia.... etc, depending on the individual fish. The best obligate aiptasia eater is a nudibranch called: Berghia verrucicornis.
here is a couple of sites you might find helpful:
http://www.wetwebmedia.com/marine/in...a/aiptasia.htm
http://www.wetwebmedia.com/nudifaqs.htm
From one rookie to another,
John