Just to further what Sadielynn said...
The grounding probe is for your fish, not you. If you're getting a shock in your tank, the grounding probe isn't the fix. The fix is finding what is in your tank that is damaged and shorting in your tank, and replacing it. Immediately. You should also have a GFCI (Ground Fault Circuit Interrupt) somewhere in your system. Either replace your normal wall outlet with one, or get one of the inline GFCIs. This will trip out long before your circuit breaker.
The grounding probe is meant to take care of stray voltage that you can't feel, but your fish can.