My husband is an electrician. If you have stray volts in your tank, and put your hand in, you can complete the circuit. This just might trip the gfci if you are lucky. However, if something starts to leak enough voltage, the ground probe will serve to trip the GFCI instead. I imagine he would explain it differently, lol, but that is my understanding. It's a safety measure he is adamnant about, or he won't stick HIS hand in there.
