I lost 12 fish to 'stray' voltage from a broken heater once about 10 years ago...that was a seriously bad day. No, I could not feel it myself in the water....and none of the breakers flipped. No GFI. Anyway, My 150 runs two vortex so there is no voltage in the tank at all.............and my iwaki is external in the basement sump........leaving only my heaters and skimmer pump as potential culprits.....and I have a grounding probe there. No issues. Good design, overpriced water pushers, and cheap probe makes all the difference. My hair stays pretty.