Random SHOCK!

[mike31154]

Don't dismiss the lights, particularly flourescents, as the cause for your tickles. Fluorescents in particular can induce a fair amount of voltage into your water via the electromagnetic fields produced by them. If you have clip on individual reflectors such as on a T5HO retro set up, make sure you ground them as well. I used to get a good tingle when brushing up against them with my hand in the water. Grounding the reflectors helped mitigate this, but there will still be some voltage induced into the water by the EMF produced by the light tube.

Here's a link with a little more in depth info. Talks about GFCIs as well and has some thoughts regarding grounding probes.

http://angel-strike.com/aquarium/GFI...alDetails.html