How do you test for stray voltage?

[MargieInAZ]

When I was working in the sump this evening I thought I felt some stray voltage. But I only felt what I thought might be stray voltage on one finger that has a small hangnail. It was a very slight feeling, and I honestly don't know if it was just saltwater hitting the nerves, or if it was actually stray voltage. When I poked my other fingers in there separately I didn't feel it at all.
I tried unplugging everything one by one and couldn't isolate anything. I really don't even know if what I'm feeling is electricity or not.
So, I guess I'd like to know if it's really obvious if you have stray voltage. Is the feeling like getting shocked by walking on new carpet where static electricity builds up? Is it sharp like that?
Or can it be very slight, almost undetectable?
Is there some sort of meter I can buy at Home Depot that would test for it?
All my fish and coral look fine.
Thanks,
Margie

[Michael]

http://saltaquarium.about.com/library/weekly/aa101602.htm

edit: heres something else from my library, it may be useful

http://www.reefs.org/library/aquarium_net/1298/1298_3.html