Boy, when I first saw the title of this thread, I was extremely alarmed and a bit shocked....
I would first recommend to unplug all the equipment you have, then plug in each device one at a time. If you have a volt meter, if would also be very handy. This will allow you to find you which device is giving out the stray current.
Also, you may sometimes experience a slight 'tingle' if your household circuits do not have a true ground. Or, it can be caused by static electricity if the tank is in a carpeted room.
I would recommend searching for "GFCI" and "Grounding Probes" here on RC and reading more about the subject.
If you have determined that it is indeed the pump that is leaking electricity, please give Danner Manufacturing a call at 631-234-5261. They will be able to tell you how to best remedy the problem (grounding the tank, wiring a true ground or replacing the pump). Danner will often request to replace the pumps themselves so they can examine your specific pump.
Please do not hesitate to contact us if you have any further questions.
Sincerely,
Joseph
Marine Depot Customer Service