You can make your own grounding wire, *for temporary use* by cutting the flat terminals off of an old plug wire from something that you don't use or is broken. Cut the cord at the device, strip the wires shielding clean so an inch or so is bare wire. Cut the FLAT terminals off the plug, or bend them back and forth until they snap off, leaving only the round ground that fits into the bottom of your outlet. Plug it in upside down (just in case you did a bad job snapping off the terminals) and run the cord into the tank. This will work for a temporary ground until you can buy a proper one. Wires are usually made of copper so you don't want to use this homemade one for a long period of time, but it could help diagnose if it is stray voltage affecting your fish...
