[GoFish]

Thought I'd share my my experience from a couple nights ago. Have never noticed any problems with the tank and never thought to check with a voltmeter.

Until I went to move some rocks around in a tank and when I put my hand in the water got zapped, turns out I had a small cut on a finger! Went outside and grabbed the voltmeter from the shed and a new Rid-volt grounding probe I had bought for another tank. Plugged the grounding probe into the power bar. First I tested from the grounding probe to the tank water and got a fluctuating reading from -.20 volts up to .30. Then put the grounding probe into the tank and tested from a ground hole in a socket to the tank water and got the same random readings! Then tested with both leads in the tank water and still got low voltage readings. I thought the grounding probe would solve it but noooo.... So where's the stray voltage coming from? I unplugged the heater, nope. The koralia power head, nope. The skimmer, nope. The aquaclear filter, nope. No single item in the tank was the cause of voltage!? So I unplugged all 4 items at the same time. STILL stray voltage! Same random readings.
I thought WTf! My GF said what about the lights? Hmmm, well they aren't touching the tank water but what the heck. Unplugged the lights and GONE! I'm using a 24" coralife T5H0 fixture, it has plastic legs that straddle the tank and sit on to of the plastic tank trim, so how does the voltage get into the tank water? I touched the legs and inspected the lights, there was salt creep all over it!
I plugged the light back in and touched the aluminum housing of the light, zap! Ah Ha!
I then looked on the floor at the plug for the lights. I had it plugged into a manual timer, and in order to do so I had to use a 3 prong to 2 prong adaptor, DOH! Kinda stupid condsidering everything else is plugged into a digital power bar. I had a power outage 6 months ago and instead of re-programming the power bar I got lazy and just used a manual timer. So I plugged the light into a proper 3 prong plug, tested for voltage again and it was gone!

Anyway, some valuable lessons learned. Test for stray voltage. If an electrical component has a 3 prong plug don't use a 2 prong adaptor (or break the ground prong off) it's probably there for a reason. Just because there's a grounding probe in the tank doesn't mean there isn't stray voltage. Salt creep really can be creepy! Use a GFCI and ground probe to be safe.

Safe reefing!