It is a heated subject. With the little E & M I've had, the only thing I can recommend is to stay away from them. Reason being is that by placing a grounding probe in, you are providing a means for that stray voltage to flow, therefore providing a current. The current that is flowing through it, combined with the voltage, is the issue. Voltage by itself isn't as much of an issue and seawater actually has a natural electrical potential due to the movement of ions in solution (which creates a very small magnetic field, too). Also, even the lights, ballasts, etc. will emit an electric field, inducing voltage in the water due to the presence of all those ions. So basically, any tank will always have some static voltage. It just seems like a bad idea to provide a means for it to move, though. Again, though, that's just the theoretical side from what I can gather.