Stray voltage - is any voltage acceptable?

After some more reading and searching on RC, I found some good info:

http://www.reefcentral.com/forums/showthread.php?t=2019240&highlight=pump+leaking+voltage

"Multimeters just aren't designed to be used in this way, theory or practice. You might have some success using them like this, but more likely than not you're going to be throwing away perfectly good equipment and running into oddities that you can't explain. If you look around here, you'll see that repeated over and over in any of the threads about this. Tons of anecdotal evidence and conflicting findings, no real science.
If there is a failure in the insulation, there will be current flowing to ground.
voltage in the tank does not mean that there will be current flowing or failure in insulation, that voltage may be "phantom" voltage due to the nature of how the meter reads and averages it's readings.
The size of the "phantom voltage" you read will depend heavily on the meter you use and the equipment that's causing it."

"What are the phantom voltages in the tank caused by water movement, electrical noise, etc? Very, very high voltage potentials, with practically no current. Well, guess what the meter is measuring? Teeny tiny currents... Depending on the size of the resistor and the sensitivity of the circuitry in the meter, there's really no telling what the meter will read. It's going to measure whatever current is there, scale it way up and try to average out a voltage.

Read current instead. That turns the meter into a wire, no large resistor, no wacky meter behavior."

And here http://www.reefcentral.com/forums/showthread.php?t=1647879

"Get a three prong extension cord.

Plug it into a nearby outlet.

Change your meter to the RED V with a squiggle over it. . The next one up from your picture's setting.

Now place one probe into the ground hole of the extension cord.

Place the other probe into the widest remaining prong slot. You should see some very low reading. Perhaps a volt or three. This is the Neutral. This is just making sure your ground is really a ground.

Now move the probe from the wide slot to the the narrow one.

You should now see something around 120V. This is the HOT.

If these last two things happened as I stated then your outlet that the extension cord is plugged into is in all likelihood correctly wired.

Now to test your tank. Before going further you need your Ground test lead to be reliable or you can make bad errors. Like thinking something that is fatally live, is not. So you should grab some masking tape or electrical tape, (not scotch or duct), and tape the probe snugly into the ground hole on the extension cord. Once this is done you should be able to wiggle the test lead a bit and not have the ground probe connection interrupted.

When done taping, again test the ground by probing the Hot again.

If that reads correctly you're set to go.

Using the free probe touch it to your tank water - read the meter.
you will likely see something like 60V or possibly even 120V. If so you have a PROBLEM.

Leave that probe in contact with the water, you can tape it somehow, (here you could use duct tape on the probe handle).

Now while checking the meter start unplugging things one at a time.

Do this until the reading plunges to very close to zero. The last thing that you unplugged was the culprit. Once you think you have the culprit always take the probe back to the hot slot in the extension cord and prove nothing has changed to cause the meter to stop working, like the ground probe has come out of contact, or a test lead has failed. Once you've re-proven the test setup you can be confident that you really found the problem.

Remove the problem completely from your aquarium setup and if it has exposed metal like a light fixture you can re-power it and then touch the probe directly to it while it's isolated from the system. This will confirm your prior test.

If it IS a fixture. Unplug it again and then examine it. You may find a frayed wire or cracked insulation, or a large salt buildup somewhere. If it is a cracked or frayed cord inspect for other age issues. Are the lamp prongs all corroded? If so you should replace all that, or pitch the entire fixture. If it's just the cord DO NOT try to repair the cord. It's a fools errand! Replace it with a new cord.

If it is a non metallic device like a heater cut the cord off of it as close to the heater body as possible so some fool doesn't try to resurrect it. Heave it in the trash and acquire a new one.

If it's something else let us know and we can help you make a determination.

I must stress that hunting for a problem like this is not without hazard. People have died while trying to find issues like this.

Be very conscious of what you are trying to do from moment to moment. Do not touch anything that might be conductive while hunting this problem. Even a salty cord could result in injury. Commonly a high resistance fault that smarts badly can be upgraded to a fatal low resistance fault because you wiggled the wrong thing or somehow increased the contact area. Don't get all entangled under the tank or bent over a sump, or rest your hand on a piece of metal or a pump while doing this troubleshooting. Approach the problem like everything is live, and out to get you, and you will be safe."

Good stuff! Hope it helps anyone that has a similar concern! If you have experiences or other tips/caveats please throw them in.

So the Faraday cage idea might be hard. Usually people use copper mesh, but it must be a metal mesh. I dont see why it would not be easier to replace your pump. Also Voltage is the difference in electrical potential. The glass tank is well insulated and therefore the whole tank is probably held at a specific potential. Its the same reason why birds on a power line don't get fried. So I doubt that any of your fish would ever feel any thing from the "voltage".

I completely understand the Faraday cage to help protect the pH probe, but I think it would be tricky. I could see that if you had a metal near the pH probe, and it was to interact with the salt water, it could totally throw off you pH reading. Plus if you used copper and it started to bleed into your tank you would have problems. 

Interesting idea! Hmmm.

Until I either buy a new pump (or whole new skimmer - I want an Elite Aquatics one!) I was thinking I could just build an acrylic "cup" or box similar to an overflow box in a way that I would somehow suspend above the sump and just start a 1/8" siphon line that had a rigid airline tube above it and a overflow that would just drip, drip, drip into the sump and never actually stay connected, thus, in theory, never transferring the voltage/current up to the probe. Also it would stay submerged since those pesky ph probes have to stay wet....

It'd take some rigging though and I'd want to have it setup so it wouldn't overflow the sump, just barely taking the top 1/2" or so of water or hey, maybe even with a durso type vent to break the siphon in the event of a power loss!!

I know, I know sounds like a lot of work but hey, I love to tinker, DIY is half the fun of this hobby for me, and besides I don't get paid for another 2 weeks!

Thanks - my sump is just a 45G tall that has a 10G drilled tank inside it that serves as my skimmer chamber and cheato box. from there it spills into the main chamber which right now has LR/LS and my return pump in it. I cut some acrylic baffles that I will be using to partition it and reverse this setup so the pump is still last but the LR is first, then probably the fuge/cheato section then the skimmer and return. Not sure which section will be best for the probe holders, probably the last one...

Anyway, I did try the concept late last night with a rigid airline suspended up above my cup that was clamped temporarily to my stand right above the sump and with an airline valve I was able to get it to just be a steady quick drip I was able to get a reading without errors. However, I am a little concerned that my readings there might be a little bit different that they would be in the tank or sump - not by much, but maybe just a little bit. As far as the flow and siphon issue - I do have an aqualifter pump that I think I'd put in line if I end up using this for more than a couple of weeks that would start and maintain the flow of water, rather than an actual breakable siphon.

Soon I will be getting my CA reactor up and going and will have a second probe in there and should have my skimmer pump replaced by then, but it's good to know that this is a possible work-around to monitor and chart my ph in the meantime.

Thanks for your participation!

Agreed - in and out of the sump makes more sense, I wonder if I just heat and bend a strip of acrylic to place over the rim of my sump and make a little "shelf" and glue in or route out a hole for my "cup" to that if It would be insulated enough... I guess I could put a couple of rubber strips under in if not!

I think you are right, I do have access to several other types of dense plastics at my "day" job, there's an interesting PVC material called Sintra that would be great, but it's got dyes in it - I have an off white version and a black version, guess I could go hit up the manufacturer's (Alcan) website and see if the ingredients are listed. Pretty sure it's just PVC, which of course we all use for plumbing so it should be safe.

Hoping to rig up something when I get off at midnight! I need my skimmer running, at least temporarily and need to have ph readings as well - I have been graphing my ph drops overnight, trying to find a good kalk drip/dose ratio to keep it fairly level until I can get a CA reactor.

Thanks for the input and ideas Mark, I did read it with the probe plugged and unplugged - there wasn't much of a difference at all. I tested it again this morning but now my cheap $10 harbor freight meter is on the fritz. I pulled out my old analog needle meter and am having mixed results with it. There is a short in the connection probe on it so I don' t really trust it's reading and unfortunately the probes between my 2 meters are not interchangeable.

I did perform a search before posting, 2 posts came up, one about the stealth heater recalls and one about a powder blue tang. Here's my search query results maybe you could take a look and see if there is something I could do in an advanced search that would yield more results?

The probe is on the opposite side of the sump from the skimmer and even moving it up to the tank still produces the error. I've tried it several times, several places with and without the probe plugged in to no avail.

Thanks for the idea of pulling that impeller out and submerging it slowly while watching the meter or my controllers display to determine if there's a crack in the housing or power cord. Maybe I can still use it if I can seal it up. It's really underpowered for my skimmer anyway and I know you don't usually run a skimmer but right now an underpowered pump on a small skimmer is better than no skimmer for my tank.

The probe works fine in a cup and it's been interesting bantering with russianrick about ideas for the "cup" to isolate the probe but ideally, yes, I'd keep it simple..

Btw - I do run my grounding probe directly to my GFCI outlet and I have half of my circulation on a separate circuit as a failsafe, highly recommend this. I've had my main circuit trip in the past (older home with questionable wiring) and been very grateful I decided to snake another power strip behind my piano to another circuit!

I do have one battery powered air pump but yes, I should get a couple of backup pumps for when I am not here. This summer has been good as far out brown and blackouts go, and the few times the power has gone out for extensive periods of time over the years I've run an extension cord out the window to my car and an inverter. Works pretty well...won't run my circulation pump or a bunch of powers dads and a heater but it keeps the water moving and aerated which is by far the most important thing in a power outage to prevent 02 depeletion, co2 buildup and ammonia/nitrate spikes from bacteria loss, right?

What did you use instead of GFCI and a probe? How are thing for you and Donna on the Big Island? Are you going to set up a tank and do NSW water changes? I would!!!

Wish I could put my tank by the window, I'm not allowed to organize the furniture lol!

KISS is a good motto for almost all things in life, I just can't seem to adopt it very well...

That's a famous overlook, I have pictures of me there 23 years ago, too bad they are only negatives in a shoebox somewhere that I'll never find.

Once Donna is ready to have a tank again and you guys get settled I'm hopeful to read about you having an "all natural Hawaiian tank" in paradise!

Most of the tanks pictured in this thread got Utah sunshine. A bright sunny south facing window is best but morning sunshine is good too. The power of sunlight, even for part of the day or indirect sunlight when the tank is close to a window creates a lot of benefits.
http://utahreefs.com/forum/forum_posts.asp?TID=37523