A few articles I've read lately
http://reefkeeping.com/issues/2005-06/sp/index.php as an example suggest that grounding probes cause more current flow in the tank, even if the voltage reading seems lower.
If you put a voltmeter on either terminal on a battery that's not hooked up you will read voltage, if you connect the two terminals, ie short circuit them you will read less or no voltage on your voltmeter. What is suggested instead is to find the peice of faulty equiptement and replace it rather than providing a rout for the "stray voltage" to escape.