I QT'ed my Copperband with a small Azure Damsel. The Azure is very peaceful (unlike some other Damsels) and was a good mate for the Copperband. He would eat the bits the Copperband left behind as I was introducing him to new foods. The Azure would never compete for food, always giving way to the Copperband, and was content with just the leftovers.
Here is a thread from a couple years ago.
http://www.canreef.com/vbulletin/showthread.php?t=73021