First copperbanded I got, he refused to eat. Just when I finally got him on frozen mysis, he was sickly and contracted ich and died shortly there after.
I refused to get one that I was going to have to train to eat frozen foods.
I finally got another 2" little guy that was going after frozen mysis in the store. Has been good ever since. He still constantly picks on the rocks, but at feeding time, he is at the top of the tank patiently waiting for food like the rest of the fish.
As far as reef compatability. Both our copperbanded never touched anything. At first we thought the one we have now was picking at the zooanthids, but then realized that he was picking between the polyps for little treats. No damage ever.
Additionally. Butterfly fish are very sociable. When ever I approach the tank, mine comes from the rockwork to the front glass and stares at me. Follows my finger along the glass, and has a very cute personality. A butterfly that hides all of the time, is timid or reserved may be a sign of an unhealthy fish.