Do grounding probes really work?

Florida Sunshine · Feb 11, 2019

I seem to remember reading conflicting reports on the usefulness of grounding probes, and I have now found myself in a situation where my husband wants to buy one so I figured I would give a shout out to R2R and see what you all think.
This came up, of course because one of my older power heads was electrocuting my tank.
We added 3 new fish on Saturday evening and everything was fine. We both had our hands in the tank etc and felt nothing.
Sunday morning I wake up and of course want to see my new fish, so I throw some food in the tank and quickly see 2 of the 3 new fish but the third (a blue eyed tang) is nowhere to be found. So, knowing that it is an algae eater, I grab a piece of nori and go to put it on the clip.
Bam, serious tingling feeling. Not pain but for sure uncomfortable. So my first reaction is to turn everything off. The tingling goes away. Of course I can't leave everything off so I one by one start plugging things in until I find the culprit and remove it from the tank.
My husbands statement was that we need to go buy a grounding probe to prevent this from happening in the future.
Is he right? Would that have prevented the electricity from going into the tank?
Oh and in case anybody was wondering, as soon as I got the electrical sorted out the tang came after the nori pretty quickly so all new members of the family are accounted for and eating.

scriptmonkey · Feb 11, 2019

Let me throw up the @Brew12 bat signal.

My novice understanding is the grounding probe would trip the breaker thus preventing electricity from leaking into the water. Of course that circuit is tripped so nothing would be running and you would need to find the offending device but nothing would be getting shocked either.

So will a grounding probe prevent electrical spillage into the water when a device malfunctions, no. Will it keep you and the inhabitants safe from getting zapped, yes, if your underlying electrical equipment is functioning and wired properly. (Breaker,outlet,wire). Brew is an electrician, so I will let him fill you in himself when he gets the time.

Flippers4pups · Feb 11, 2019

I run one. Thing is with electricity it will follow the path of least resistance. Even with a grounding probe, anytime you place you hands in the water you should be wearing shoes. GFCI on all your lines for the tank is absolutely needed.

Dom · Feb 11, 2019

This subject has been heavily debated many times that I recall here on R2R. I think it comes down to personal priorities.

Voltage doesn't kill. Current kills. So without a grounding probe, you may have voltage, but no current. When you add a grounding probe, you now have current because you are creating a path for electricity to travel out of the tank.

When you get zapped, it is because you have created a path out of the tank for electricity by placing your hand in the tank and your feet touching the floor. But if you have sneakers on, the rubber insulates you from the floor, eliminating the path.

In my opinion, it should be safety first! If you have kids around the house, there will be curousity and some mischief. It isn't unreasonable for them to want to stick their hands in the tank (and if you use a sump, you will have electricity there too).

I use a probe. I love my fish and spend good money to buy them and keep them. But I'd rather lose a fish than a family member.

So to answer your question, yes they work.

Florida Sunshine · Feb 11, 2019

So which is more harmful for my tank inhabitants? Current or Voltage? I'm not so worried about me because you are right I could have prevented my shock just by wearing shoes and I have no children in the house. I am more worried about protecting my fish etc.
That actually does bring something else to mind though. When we were messing with the tank Saturday night we were both likely wearing tennis shoes since we had just gotten home. I was convinced this just started because we felt nothing on Saturday when now it seams it could have been going on for some time.
I believe you have convinced me of the usefulness of the grounding probe for safety, but will that protect my fish from electricity that may be leaking into the tank from another piece of equipment or is there something else I need to do to prevent future mishaps of this kind?

Dom · Feb 11, 2019

I've been using a grounding probe for years in all of my tanks. My fish and corals thrive. And when I have issues, it's never been stray voltage.

Brew12 · Feb 11, 2019

Thanks for the invite!

scriptmonkey said:
My novice understanding is the grounding probe would trip the breaker thus preventing electricity from leaking into the water. Of course that circuit is tripped so nothing would be running and you would need to find the offending device but nothing would be getting shocked either.

This is true but it would take a catastrophic failure to occur. You would need to pull 20A+ to get the feeder breaker to trip.

Flippers4pups said:
I run one. Thing is with electricity it will follow the path of least resistance. Even with a grounding probe, anytime you place you hands in the water you should be wearing shoes. GFCI on all your lines for the tank is absolutely needed.

This is my preferred method. As soon as a piece of equipment begins to fail the ground probe/gfci combination will trip with only .005A of current.

scriptmonkey said:
So will a grounding probe prevent electrical spillage into the water when a device malfunctions, no.

+1 on this. A ground probe alone will not prevent electricity from entering the tank.

Florida Sunshine said:
I believe you have convinced me of the usefulness of the grounding probe for safety, but will that protect my fish from electricity that may be leaking into the tank from another piece of equipment or is there something else I need to do to prevent future mishaps of this kind?

Florida Sunshine said:
So which is more harmful for my tank inhabitants? Current or Voltage?

This is a tricky subject. For us, current is the problem but we live in air which is an insulator. For fresh water fish, current is also the biggest issue which is why electrofishing works. The saltwater in our systems is much more conductive than the fish so current will flow around them instead of through them. This is why you can't electrofish in brackish or salt water. Voltage is a bit more complicated and typically only matters when you are talking about comparing one voltage to another. For instance, if you are wearing rubber soled shoes and grab a 120V wire you have gone from ground voltage to 120 volts but you would never notice or feel anything. People who work on high voltage lines via helicopter are raised to 500,000+ volts with no health issues. I'm not comfortable saying voltage has no impact on fish because there could be a problem with tiny voltage differences due to turbulent water but I personally feel it is unlikely. There is some anecdotal evidence that voltage can cause HLLE issues in fish but it hasn't been confirmed.

Dom said:
This subject has been heavily debated many times that I recall here on R2R. I think it comes down to personal priorities.

It is very heavily debated and there is also a lot of bad information out there making the topic even more confusing. I fall on the side of being a big fan of using the ground probe/GFCI combination and I do it more to protect my fish than personal protection. My concern isn't the voltage or the current, it is the contaminants. If you have a powerhead or heater failing in your system, you will most likely have exposed copper wiring (although it could be aluminum). Metals will corrode faster when energized causing more to leach into the water. It can also generate heat and/or release other toxins into the water. To protect my fish and coral from these contaminants I want whatever is failing to de-energize as quickly as possible. This also lets me know I have a potential problem much earlier than the 2 weeks I may go without putting my hand in the tank.
The biggest argument against using a grounding probe/GFCI combination is that it may trip while you are away from home. This can cause issues more quickly than the leaching copper. I feel this can be compensated for through design. In my system, I run with 2 GFCI outlets. My tank will be fine for at least a day or two even if one trips because of how I have my loads spread out. I show what I did here.
https://www.reef2reef.com/threads/diy-gfci-installation.342874/

The other thing this does is lets me change out the GFCI's in case one fails. My main outlet that powers my tank is behind my tank and would be impossible to work on. GFCI's will go bad over time so this makes one less thing for me to worry about.