Awesome fish. I am thinking of buying another one and nearly did today.
So the pros and cons of the fish. Once you buy one that is eating Mysis, I suggest you toughen it up by allowing it to hunt. What I mean by that is to drop a half cube or whatever in the tank and make him go get it with the powerheads on. New fish rarely eat on the first day but he should get the hang of it. You may need to use a baster and kill the powerheads though. Some are finicky.
I had two Copperbands in the past. One was great and I had him for over 6 months but he decided to stop eating and give up in life once I introduced a Clown Tang in the tank. He was never picked on, but he was always intimidated by how fast the Clown Tang swam.
My second Copperband never made it. He refused to eat even after I watched him eat at the LFS.
So the Pros would be they are awesome and like my first one, they CAN eat Aiptasia. But it is a hit or miss.
Cons - They are bipolar and can all of a sudden stop eating whenever they want.
Hope I am not rambling too much, my son is crying for me. Gotta go.