If petstore's are treating with copper, and you buy a fish and bring it home...but make sure that no water from the bag gets in your tank. Are you safe?? thanks
before you wipe down your fish you should set it on a breadboard and run a rolling pin across it to squeeze out any excess water or feces that may contain copper as well
or you could just get a copper sponge from your supplier. I have not tried one of these but have seen them in the stores