Can you post the settings you used on the voltmeter to get this reading? I'm curious...have a voltmeter...but am unsure on how to set it to get a proper reading.

No problem. I used a standard mastercraft voltmeter set to the 200V AC setting. On my meter it looks like this:
~
V

If your meter has a lower setting, you could probably use that to get better resolution but as it is, it gave me an accuracy down to one decimal place(pending the voltmeter is actually calibrated correctly)

I put the probe from the V/Ohms/mA port and placed that in the water running through my sump, and placed the ground probe in the ground socket of my powerbar that my skimmer pump runs on.

After leaving the probes in the water for a while, the voltage would fluctuate from 1.9 V up to 3.6V depending upon what electrical appliances were running at the time.

Hope this helps

Untamed, did you get a voltage reading from your tank yet? Just curious to see what other peoples systems are running at.

OK...my voltmeter seems similar to yours. Set the way you describe, I get a reading of 0.4

The reading doesn't change if I remove the ground probe that I have.

GFI extension cords? What does one of these things look like and where do you get one?

You can get a 4 outlet Noma GFI powerbar at Canadian tire for just over $20. You can also get plug in ones with single outlets you can then plug a power bar or something into. We started stocking them at work recently, they're a bit cheaper and pretty decent.