I wouldn't use copper by any means. There are far too many alternatives. Aiptasia X Worked in one shot for me when I had tons of it. I had two that were pry 5", gave'em a good shot and , poof!, gone. I also bought two peppermint shrimp that eat all of the little ones. I've heard of boiling water basted onto them too, but that didn't work for me. Really though? A coil of copper wire in your sump?