I'll agree, the copperband isn't always a good eater when it comes to keeping them. I tried using a copperband once with an aiptasia outbreak and I was quite impressed with how well he took it out, but afterwards he refused to eat anything I gave him and ended up losing him due to self inflicted starvation.
As for the comment about using natural predators for contolling of problems, I'll agree that it's best to avoid the problems all together, however in my case, I didn't see any aiptasia in my tank for upwards of 2-3 months after placing the live rock in and I can't imagine one would quarantine anything for that length of time in order to ensure it to be free of nasties, unfortunately in my case, as I'm sure that it rings true for many beginners is that you see something new and are in awe that your successful in propogating new life in your tank that you don't always recognize it as being a problem until it gets to be too late and the only options you have are natural predators, rock cooking or dumping everything and starting over.