I keep a Copperband to keep aptasia at bay as well. The Copperband won't actually eat the aptasia he will just keep it closed and starve it. Chances are when/if the copperband dies some of the aptasias will re open. Only thing I've ever seen actually devour the entire thing is peppermint shrimp.
Beware... Occasionally once the aptasias are all closed the Copperband will develop a taste for your brains. said:
That's strange, the CBB's I've had have all eaten aiptasia as in nothing left in that spot, actually seen them attacking them. I have also had rock's in the garage with no light or food for months and the aiptasia was still alive, white but still very much alive. I have heard of then eating acan's etc., but I have not had that issue....yet and they alway's had plenty of choices in each tank that I have had. [smilie=smile.gif]
Cheers,