Using Ground Probes in Aquariums

[Reef_Obsessed]

After reading this write-up, I will be searching for a grounding probe later today. Thanks for the info.

One question: I live in Japan and all of Japan utilizes a 2 prong plug system. While building my house, I ordered 3 prong sockets from the US and had the electrician install all 3 prong plugs in my tank area. Is this what you are speaking about when you mention GFCI?

 

[thermoJoe]

Thanks. I currently have a rubber mat in front of the tank, but I think I'll have to get a grounding rod too. Perhaps add a current meter too.

 

[vetteguy53081]

After reading this write-up, I will be searching for a grounding probe later today. Thanks for the info.

One question: I live in Japan and all of Japan utilizes a 2 prong plug system. While building my house, I ordered 3 prong sockets from the US and had the electrician install all 3 prong plugs in my tank area. Is this what you are speaking about when you mention GFCI?

Gfci is a ground fault interrupter that would trip and cease power in the event of electrical overload . There are probes that wire to your outlet ground eliminating the need for a socket

 

[SteveC]

Hi,

I agree with Brew and using a ground probe to keep us safe. A great article, and I do not want to degrade your work BUT your statement “Electricity always takes the lowest resistance path to ground.” Is not correct. It’s why we have parallel circuits. E.g. if you have some lights of different resistances ( wattages )at home , the current does not just go through the light with the lowest resistance ( wattage ) and all others that are in parallel fail to light up. The different resistance ( wattage ) bulbs will also light up and carry current according to their individual resistances ( wattages ) . Also, why lightning bolts are not just one single path to earth.

Given that, when we put our hands in a tank and provide an Earth for any voltage applied to the water, the fish could very well feel a bit of a shock. But not as much as we would! ( the fish are a parallel circuit ).

I’m sure, Brew wrote what he did in simplification. I’m only correcting a technical error and agree wholeheartedly with ground probe use. Especially if you live in an older property with older vintage circuit protection.

 

[Don Lidtke]

I am two grounding probes to GFCI; one with the heaters and the other with the return pumps. I ended up with two so I saw no reason to not use the both. Hope I am not being silly.

 

[SteveC]

No, not silly. The more the merrier!

 

[Hybrid Ken]

Where did you order from?

Marine Depot has them.

 

[DocPaulo]

Titanium probes in amazon... works great

 

[Greg Gdowski]

Great thread. "You cannot shock a marine fish while it is in salt water since the water is more conductive than the fish." True, but I'm not sure that is really the right message. Its sort of like a car battery. You can touch one lead or the other -- as long as you are not touching both and creating a circuit -- then you are safe. When you put a ground probe in the water -- it is ground (sounds stupid -- right?). However, keep in mind --- if you pull that device out of the water while its plugged in and on --- and you have your other hand in the water (ie ground) -- you will be shocked. That is why ground probes can be dangerous. They give the misconception of ultimate safety. Presumably the GCFI will trip and save this event from happening. I would prefer to have a ground probe with some sort of indicator that tells me when a problem is just starting to happen. That way I would know to turn off all the power, even when there is a remote chance of shock. Again -- good thread (very stimulating ).

 

[Brew12]

That is why ground probes can be dangerous. They give the misconception of ultimate safety.

I believe I understand where you are coming from, but to offer clarity, it is not the ground probes that are dangerous. It is the misconception that they can prevent all electric shocks in every situation.

However, keep in mind --- if you pull that device out of the water while its plugged in and on --- and you have your other hand in the water (ie ground) -- you will be shocked.

This is true. But, you will also get shocked if you touch any device with a 3 prong plug such as a light fixture, ballasts, metal housed power supply or even if you are standing barefoot on a non insulated surface. I would not recommend cutting off the ground prong on one device in order to prevent it from being a path to ground in the event I touch it while holding a failed device in my other hand.

 

[Brew12]

I do not want to degrade your work BUT your statement “Electricity always takes the lowest resistance path to ground.” Is not correct. It’s why we have parallel circuits.

You are absolutely correct, this was as an oversimplification. Current will flow to ground based on the impedance of each path to ground. If you take the typical wet body resistance of 1,000 ohms and a relatively poor ground connection at 0.1 ohms you will get 10,000 times more current through the ground path than through a person. If you had 20A flowing through the ground probe and you put your hand in the tank you should see no more than 0.002A through your body which shouldn't even be enough to trip a GFCI. Even if you have a freely bleeding cut your resistance would be 300 ohms or more for a max current of .007 amps which you could feel but wouldn't be dangerous.

I did the same math before to see how it would impact a fish so I'm going to be lazy and cut and paste my post from a different thread.

"When we put the fish and the water in parallel we know that current will flow in relationship to the conductivity of the path. For this part, I will assume we are limited to 20A by a circuit breaker. Resistances in parallel are added this way.

where the inverse resistance of the water (R1) is 5 and the fish (R2) 0.00114 for a total inverse resistance of 5.00114. When we do the inversion we get a total resistance of 0.19995 (notice how close this is to the 0.2 of the seawater?) Again, using V=IR we can solve for the voltage drop across both the fish and water at the maximum 20 amps (V=20*.19995) which is 3.999 volts. Now we can calculate the total current in branch going back to V=IR (or, I=V/R properly arranged). For the water (I=3.999/0.2) we get 19.995 amps. For the fish (I=3.999/875) we get .005 amps. "

So, yes, current will take multiple paths but for the purposes of this discussion the amount of current, even in a worst case scenario, is fairly negligible.

 

[vetteguy53081]

 

[SaracensRugby]

Hi all, not to be a fly in the ointment here, but to provide a different view from what I read in The Reef Aquarium: Science, Art, and Technology by Delbeek and Sprung (pg 131). The URL they provide in this book no longer seems to be active, from a study at a university, so I will try and paraphrase here from what is said in the book. Anecdotally, I tried a grounding probe and saw adverse reactions from my fish, and I put the probe in my sump. My 2 clowns jerked erratically a lot, where they didn't before. I took the probe out after a couple days, back to normal. Again anecdotal in my case, so see below analogy from the textbook.

"A bird can sit on a power line with 10000 volts and not be harmed. If another bird is sitting on another power line directly above said bird (on a 10000 volt wire), and these birds touch, a current will pass through the body of the bird on the lower wire, killing it instantly, while the bird on the higher wire experiences extremely damaged feet. So adding a grounding probe in a tank provides a current path that did not already exist. A fish that passes between the source of voltage and the probe will experience an electrical current. With a grounding probe, the creation of a current path could worsen the situation for the tank inhabitants."

The material in quotations is taken from the textbook, albeit paraphrased a bit to save me time.

 

[Brew12]

Anecdotally, I tried a grounding probe and saw adverse reactions from my fish, and I put the probe in my sump. My 2 clowns jerked erratically a lot, where they didn't before. I took the probe out after a couple days, back to normal.

I appreciate your sharing this. I would love to have more information and you aren't the first person who mentioned something like this happening. Did you use a GFCI? Have you ever had an ICP test done?

A bird can sit on a power line with 10000 volts and not be harmed. If another bird is sitting on another power line directly above said bird (on a 10000 volt wire), and these birds touch, a current will pass through the body of the bird on the lower wire, killing it instantly, while the bird on the higher wire experiences extremely damaged feet. So adding a grounding probe in a tank provides a current path that did not already exist.

I would argue that anyone who uses the bird on a power line analogy in reference to a reef tank does not understand what they are talking about. The analogy does not work because birds live in air, an insulator. Marine fish live in saltwater, a conductor.

I show some simplified math above on just how little current would flow through a fish even if 20 amps of current were flowing from a fault in the tank to the ground probe. You can see it if you look up 2 posts. If you would actually do the math in a complex model, the actual current flow be much less do to the cross sectional area of the water.

 

[SaracensRugby]

I had my probe plugged into a GFCI extension cord, got it from Amazon or some place like that. Wasn't too cheap if I recall. And my sump was through a wall in my closet (behind the tank), which I found weird that my fish reacted the way they did to be honest.

I had the ATI version of ICP test done a couple months ago, on my newer upgraded tank (that included all livestock/rock from old tank), and all parameters reported as normal. Almost wish I had something off to explain some of my SPS frag loss

And just a point of explanation in the event it wasn't clear above, as I have no real knowledge of the in depth technical side of electrical current, the birds would have to touch to create that current between them. I enjoy reading all of this, helps further my understanding of these topics.

 

[Brew12]

I had my probe plugged into a GFCI extension cord, got it from Amazon or some place like that. Wasn't too cheap if I recall. And my sump was through a wall in my closet (behind the tank), which I found weird that my fish reacted the way they did to be honest.

Just so you know in case you ever go down this path again in the future, the ground probe doesn't need to get plugged into a GFCI outlet. The probe can be plugged in anywhere and it will still perform its intended function. I recommend powering the electrical equipment in your tank with a GFCI or 2, or 4 like I had at one time.
If whatever caused your issue is still possibly there you will want to be careful not to use a titanium heater with a 3 prong plug. They act exactly like ground probes.

 

[Brew12]

And just a point of explanation in the event it wasn't clear above, as I have no real knowledge of the in depth technical side of electrical current, the birds would have to touch to create that current between them.

I'm very familiar with the analogy so yes, that was clear. I'll try to do a better job explaining why the analogy doesn't work. The power line the one bird is sitting on is at a different voltage than the power line the 2nd bird is sitting on. They touch and the birds are shocked. This happens because the two power lines are electrically isolated from each other. We can't have 2 power sources electrically isolated from each other in our marine aquariums since the water electrically connects everything together.
Think of it this way. The bird is sitting inside a copper pipe that is at 10,000V with current running through it. A second bird flies into the pipe and touches the first bird. Does anything happen? Probably not. It also doesn't matter how much current is running through the copper pipe. The fact that the birds are both completely enclosed by the copper pipe, like fish are by salt water, makes it so they will always be at almost the exact same voltage. Since the copper is much more conductive than the birds, the current stays in the pipe. In our aquariums case, since the salt water is much more conductive than the fish, most of the current stays in the water and goes around the fish.

Hope that helps.

 

[SteveC]

What do we do if we don't have grounded outlets in our home?[

You are absolutely correct, this was as an oversimplification. Current will flow to ground based on the impedance of each path to ground. If you take the typical wet body resistance of 1,000 ohms and a relatively poor ground connection at 0.1 ohms you will get 10,000 times more current through the ground path than through a person. If you had 20A flowing through the ground probe and you put your hand in the tank you should see no more than 0.002A through your body which shouldn't even be enough to trip a GFCI. Even if you have a freely bleeding cut your resistance would be 300 ohms or more for a max current of .007 amps which you could feel but wouldn't be dangerous.

I did the same math before to see how it would impact a fish so I'm going to be lazy and cut and paste my post from a different thread.

"When we put the fish and the water in parallel we know that current will flow in relationship to the conductivity of the path. For this part, I will assume we are limited to 20A by a circuit breaker. Resistances in parallel are added this way.

where the inverse resistance of the water (R1) is 5 and the fish (R2) 0.00114 for a total inverse resistance of 5.00114. When we do the inversion we get a total resistance of 0.19995 (notice how close this is to the 0.2 of the seawater?) Again, using V=IR we can solve for the voltage drop across both the fish and water at the maximum 20 amps (V=20*.19995) which is 3.999 volts. Now we can calculate the total current in branch going back to V=IR (or, I=V/R properly arranged). For the water (I=3.999/0.2) we get 19.995 amps. For the fish (I=3.999/875) we get .005 amps. "

So, yes, current will take multiple paths but for the purposes of this discussion the amount of current, even in a worst case scenario, is fairly negligible.

I agree.

 

[SteveC]

Hi all, not to be a fly in the ointment here, but to provide a different view from what I read in The Reef Aquarium: Science, Art, and Technology by Delbeek and Sprung (pg 131). The URL they provide in this book no longer seems to be active, from a study at a university, so I will try and paraphrase here from what is said in the book. Anecdotally, I tried a grounding probe and saw adverse reactions from my fish, and I put the probe in my sump. My 2 clowns jerked erratically a lot, where they didn't before. I took the probe out after a couple days, back to normal. Again anecdotal in my case, so see below analogy from the textbook.

"A bird can sit on a power line with 10000 volts and not be harmed. If another bird is sitting on another power line directly above said bird (on a 10000 volt wire), and these birds touch, a current will pass through the body of the bird on the lower wire, killing it instantly, while the bird on the higher wire experiences extremely damaged feet. So adding a grounding probe in a tank provides a current path that did not already exist. A fish that passes between the source of voltage and the probe will experience an electrical current. With a grounding probe, the creation of a current path could worsen the situation for the tank inhabitants."

The material in quotations is taken from the textbook, albeit paraphrased a bit to save me time.

Brew, could this be some sort of battery effect? SaracensRugby, do you use any D.C pumps in your system.

 

[Greg Gdowski]

I believe I understand where you are coming from, but to offer clarity, it is not the ground probes that are dangerous. It is the misconception that they can prevent all electric shocks in every situation.

This is true. But, you will also get shocked if you touch any device with a 3 prong plug such as a light fixture, ballasts, metal housed power supply or even if you are standing barefoot on a non insulated surface. I would not recommend cutting off the ground prong on one device in order to prevent it from being a path to ground in the event I touch it while holding a failed device in my other hand.

Yes that is correct.