Bill when you check between your grounded terminal(White) and grounding terminal (green) on your duplex receptacle, is there any voltage? In the times of drought like now, we tend to lose our service ground or it gets weak. The only bad thing about a grounding probe is if you lose your service ground or it gets weak it will use your aquarium as a grounding path. (We will not mention a lightning strike)This happened to one of our LFS owners and with only 5 volts it would shock the heck out of him. General note in times of drought, soak the ground where your ground rod is installed.