Stray Voltage?

[Reef Pilot]

I used to have a T8 canopy light fixture sitting on top of my refugium/QT that was producing stray voltage in the tank. I don't know exactly how that was happening, as the canopy was not in contact with the water, just sitting on top of the glass tank. It was plastic, too. But when I turned it off the stray voltage would disappear, so it was definitely happening.

I also had a few different pumps that would produce stray voltage, so now just have ground probes in everything. No more stray voltage.