Ground probing is not good for the tank.
When there is a slight elec. fault such as proven by tingling, normally the tank doesnt get earthed unless you are working on it.
if you run a probe continuosly there is a chance you are CONTINUALLY
grounding all the tank inhabitants also.
There will be potential differences between one end of their body and the other.
Its probably usually too small too affect them, but if something does fault whilst a ground probe is attached there is a chance they could be fried.
I get fairly heavy tingles if i work on the tank/sump with no shoes on.
the current goes straight through me into the ground.
I hate it, but still wont use a ground probe OR RCDs.
Too easy to fault and kill power to the tank.