I think you need it in your tank. Let the heater get it's own ground probe. The GFCI would have tripped if there was a ground probe, if not, the thing is defective and you can remove it and use it as a door stop or paperweight.
Jcdeng, copperbands and quite a few other fish are considered hard by many people but they are not hard at all. People just don't feed them correctly. Also (and I know I will make a lot of enemies for this) if you quarantine copperbands, they will hate you as they do not like small, bare tanks. No way, not at all, never. They also must eat meaty, whole foods every day as they won't eat flakes, pellets and Happy Meals which IMO should not be fed to anything. It is true that I can't keep copperbands as long as most other fish, but I can usually get 8 or 10 years from them which isn't great, but it isn't bad either. I think I can but they seem accident prone and are jumpers. Their delicate snout is also easily damaged. Copperbands also suffer during collection from internal injuries and often have internal bleeding when we buy them. (You need to autopsy them to find that but after an autopsy, they don't fare to well)
I wrote an article about them (If I am allowed to link it here, if not, delete it)
CBB love worms most of all which is missing in a lot of marine foods. Unless you have well established populations in your rock that can handle the predation they run out of food to graze on while your away. Mine loved when I rotated rocks full of feather dusters out of the sump on special occasions.