Voltage - EMERGENCY-

Don't know if that is the problem, but pull things out until the voltage goes to 0 to find the leaking device. Then trash it.

 

I was having the same questions not to long ago. http://www.greateriowareefsociety.org/Community/DiscussionForums/tabid/78/aft/22573/Default.aspx
I'm not sure if your saying you have 5 volts when you tested, but that isn't very much. Everyone emphasized that amps were more of an issue, so check those.

 

http://joejaworski.wordpress.com/2007/09/06/aquarist-found-dead/

Good read!

 

You cant check amps like that. Amps are the current or flow of electricity, voltage is the energy. Lets put it in plumbing terms. Voltage is the amount of water going thru a hose or GPH. Amperage is the force of that water. Resistance is the size of the hose. If you have 100gph going thru a 1/4" hose the current will be fast and hurt. If you have 20 gph goin thru a 1/4" hose the current won't be as fast and won't hurt. So 5 amps isn't something to worry about because even if you put your hand in there and 10 amps of current flow thru you, it's only flowing at 5 volts.
Now I'm not saying to leave it be, you should still try and find the problem, but I don't think this is what's killing everything. IMO

 

Here's an article on GFI's in aquariums, and NOT recommending the use of a ground probe as well.  Evidently, the probe could defeat the purpose of the GFI. 
GFI:
http://angel-strike.com/aquarium/GFI&TechnicalDetails.html
Article on stray voltage and ground probe:
http://angel-strike.com/aquarium/GroundingProbes.html

 

Just a thought, but if there is something leaking electricity into the tank, it could also be leaking harmful chemicals, heavy metals, etc. from the faulty, corroding appliance.

 

So is all your equipment plugged into a GFCI?  If not then I suggest installing one, then you can plug each piece of equip. in  individually and see if one is shorted, it'll trip the GFCI. 
I would also suggest a ground probe because while your livestock can be replaced, your life can't. If you don't have a place for stray voltage to go, i.e. ground probe, and you stick your hand in the tank then you become the path, given your grounded.

 

Sparky.....question.

GFCI. My equipment is NOT plugged into a GFCI. I don't trust them to work. In other words, I think it is very likely the GFCI will fail unnecessarily, crashing my tank.

I do use a ground probe however.

Your thoughts.

 

I totally understand where your coming from.

First, if you buy a quality GFI, ie. more expensive ones, then you should have no problem with unnecessary tripping. Only if you have a faulty piece of equip. would the GFI trip, signaling that somethings wrong.

Two, having a ground probe is good but without a GFI, you won't know if somethings wrong. The current will simply travel safely thru the tank and out the ground probe. Electricity takes the shortest path and path of least resistance. So lets say you have a faulty PwrHead and the current is grounding out via the ground probe, safely. Unknowingly you are a shorter ground path and you stick your hand in the tank. OUCH! With a GFI you would have known, "hey, my powerheads off, the GFI tripped, maybe somethings wrong."

What I would suggest, if possible, would be to install multiple GFI's. This way if some faulty equip trips a GFI it won't take out the whole tank, just whats plugged into that outlet.

My suggestion would be at minimum to use a GFI. If a piece of equip. is faulty then it will trip, saving your life. Ideally use multiple GFI's and a ground probe.
You could also just plug the ground probe into a GFI if you don't trust them. This way if a fault is detected the GFI will trip indicating to you somethings wrong, without taking out everything. Your equip can still be plugged into normal outlets. However there will still be electricity in the tank flowing thru the ground probe but you would know because the GFI is tripped. Get a GFI with a lighted indicator also, easier to see when/if it trips.

Hope this helps.
PS. depending on where u live I could help ya out. I trade labor for frags.

 

Good info Sparky

 

Thanks Sponge. I've been an electrician for 8 years and had to take continuing ed classes in order to keep my license. If  I asked all the electrical inspectors, what piece of electrical equip. saves the most lives? They would say a GFI, by far.
Heres a story from one of the inspectors who holds most of the continuing ed classes here in Lincoln. I've heard it multiple times and it gives me chills each time.
He got called to investigate an electrical death. It was a guy who had a shop where he mounted those running lights under cars, red, green, etc. Well what happened was he had an old corded metal drill, the whole thing was metal, no double insulation. At some point the ground prong broke off the cord and since the drill was so old the cord was not polarized. Polarized meaning you can only plug the cord in one way, hot to hot, neutral to neutral. Well the cord was not polarized and the ground prong was gone, so he plugged it in backwards, hot to neutral, neutral to hot. The neutral was bonded to the casing which would be bonded to the ground. He then laid under the car on a metal drain grate, ie perfect ground, and pulled the trigger.
When the inspector got there to look at the drill, he could see the guys hand print burned into the side of it. The guy died. Had that drill been plugged into a GFI it would have sensed an imbalance in load, and instantaneously tripped saving his life.
This is why GFI's are required to be used in kitchens, within 5ft of a sink, in garages, unfinished basements, outside, and to protect devices in wet locations. All these areas pose an electrocution threat.
Be safe and happy reefing. (stepping off the soap box)