Incidentally, yesterday I got a call from a tank I assist with that one of the Jebao power heads stopped working. I was like "big surprise" but needed to go there anyways. When I reached into the overflow box to grab the magnet, my arm brushed the light fixture and tingle tingle
When I unplugged the controller for the power head and plugged it back in, it sparked a bit, just a bit more than your typical spark you get when you plug in a barrel connector...not sure if that is why the pump was going bad, but that wasn't the bad piece of equipment, as I soon discovered.
I removed the power head completely, then I went to clean the algae scrubber and when I was reaching into the box (water off, screen removed) I got it again. So I started unplugging things one at a time and probing...skimmer pump was bad.
Incidentally, no GFCI on this tank, no ground probe either. Not my choice, setup is existing. Going to need to do some eval and make some suggestions...