Here’s my two copper penny’s’ worth. Remove the carbon, after a week it’s probably removed all it can. Continue w/ the water changes – dilute, dilute, dilute. (never stop them, as long as you have fish, do regular water changes) Be sure to barrel out the gravel. Watch your ammonia levels, I’m thinking that the copper has killed some of your biological filter, which now has to reestablish itself. Copper can be tricky, what happened that you treated w/ it?
http://www.aquarium-medications.com/
http://www.peteducation.com/article....+2154&aid=2657