Who has a grounding probe in their tank?

[Leah]

I have a question, I have 2 grounding probes and when the electrician was here doing
some work, I asked him about the testing, that is mentioned in the instructions. He had
no idea what it was talking about. So they are still sitting in the closet. Iam also a bit
confused as how they could zap the fish. Do they absorb stray voltage, Iam confused.
Please explain for us dumbies.