Acropora and Stray Voltage

[H@rry]

How much stray voltage is too much for Acropora? I can test from time to time and get between 1.5V and 0. I do have a ground probe. Some of the Acros have developed burnt tips and some STN. I've checked PO4 @ .07, Nitrate @ 2, Alk @ 9.1. Trying to find an answer to a problem. Montiporas, Stylopora, Bird Nest, LPS and fish seem fine.

 

[billyocean]

How much stray voltage is too much for Acropora? I can test from time to time and get between 1.5V and 0. I do have a ground probe. Some of the Acros have developed burnt tips and some STN. I've checked PO4 @ .07, Nitrate @ 2, Alk @ 9.1. Trying to find an answer to a problem. Montiporas, Stylopora, Bird Nest, LPS and fish seem fine.

Burnt tips are from high alk and low nutrients .07 is ok for p04 but n03 at 2 is too low at 9.1 IME.

 

[Randy Holmes-Farley Verified Community Expert]

I think there is a ton of misinformation about voltage measurements in reef aquaria and what causes it and what it causes, but I do not think your situation suggests any concern for corals from what you observe.

 

[gbroadbridge]

How much stray voltage is too much for Acropora? I can test from time to time and get between 1.5V and 0. I do have a ground probe. Some of the Acros have developed burnt tips and some STN. I've checked PO4 @ .07, Nitrate @ 2, Alk @ 9.1. Trying to find an answer to a problem. Montiporas, Stylopora, Bird Nest, LPS and fish seem fine.

I'm not even sure I understand what people mean by stray voltage as the term is pretty meaningless.

If you have a working ground probe in the tank water (by that I mean a probe that is correctly connected to the house ground used by the electrical utility supplier), any measured AC value is most likely to be inductively coupled from wiring to devices in the tank.

If there is any significant current flow from an electrically 'leaky' mains powered device, it would trip an RCD/GFCI before it would cause any issues with animals in the tank.

 

[Salty_Northerner]

I'm not even sure I understand what people mean by stray voltage as the term is pretty meaningless.

If you have a working ground probe in the tank water (by that I mean a probe that is correctly connected to the house ground used by the electrical utility supplier), any measured AC value is most likely to be inductively coupled from wiring to devices in the tank.

If there is any significant current flow from an electrically 'leaky' mains powered device, it would trip an RCD/GFCI before it would cause any issues with animals in the tank.

Correct me if I'm wrong but I believe a GFI is ONLY going to protect you if there is voltage in the water and you going to stick your hand in the tank. That is when a GFI will actually trip.

Say for instance your heater breaks in the tank the GFI will not trip because there is nothing to break the circuit unless voltage finds its least path of resistance to ground. But maybe a grounding probe will cause it to instantly trip but from my understanding if there is no GFI hooked up but you do have a grounding probe it should trip the breaker in the electrical box. Here I'll paste this for better understanding.

A person would assume that if a kitchen mixer falls into the sink filled with water, the GFCI should trip, preventing any accidental electrocution. If the mixer is immersed in water to the extent that water is in contact with the electrical parts, current will flow from the “hot” conductor into the water. Then, unless there is a path to ground, the same amount of current will eventually flow back to the GFCI through the “neutral” conductor. The GFCI will not detect any difference in current flow, and will not trip the circuit off. But, current will circulate through the water looking for the lowest impedance path.

 

[gbroadbridge]

Correct me if I'm wrong but I believe a GFI is ONLY going to protect you if there is voltage in the water and you going to stick your hand in the tank. That is when a GFI will actually trip.

Say for instance your heater breaks in the tank the GFI will not trip because there is nothing to break the circuit unless voltage finds its least path of resistance to ground. But maybe a grounding probe will cause it to instantly trip but from my understanding if there is no GFI hooked up but you do have a grounding probe it should trip the breaker in the electrical box. Here I'll paste this for better understanding.

A person would assume that if a kitchen mixer falls into the sink filled with water, the GFCI should trip, preventing any accidental electrocution. If the mixer is immersed in water to the extent that water is in contact with the electrical parts, current will flow from the “hot” conductor into the water. Then, unless there is a path to ground, the same amount of current will eventually flow back to the GFCI through the “neutral” conductor. The GFCI will not detect any difference in current flow, and will not trip the circuit off. But, current will circulate through the water looking for the lowest impedance path.

The OP stated that they have a ground probe in the tank.

If there are any significantly electrically leaky mains powered devices in the tank, current will flow from active to the ground, tripping the GFCI.

If there is no GFCI the amount of current that would flow will likely but not definitely trip a normal circuit breaker.

Measuring incidental voltage is pretty much useless in any body of water which has a mains powered device submersed in it as there may well be 10's of Megohms of resistance limiting current flow.

 

[Salty_Northerner]

Grounding probes in an aquarium is still questionable. Also how is the op measuring stray voltage?

And I personally know from a mishap that happened a number of years ago where my cat knocked my light into the aquarium and it never did trip the breaker in the junction box.

And he was reading 1.5 volts and sometimes reads 0 voltage.

There's too many questions to really assume what's going on like how old is the house, does he have a GFCI where he's drawing is power from? Also what country is the individual living in and what are their building codes. But I get what you're saying and it's not going to argue the fact. Just we need more information.

 

[Randy Holmes-Farley Verified Community Expert]

A few folks have noted HLLE effects on fish that went away with a grounding probe. Whether that is real or not, I do not know, but similar effects are not noted for corals that I have seen.

Since we are getting into a detailed discussion, here's my comment on stray voltage from a previous post.

To be honest, there's a lot of commentary around this issue and almost no evidence.

There is also a lot of different opinions of what stray voltage and current even are in a reef tank.

I'll make a few comments...

1. What folks often refer to as "stray" voltage is a voltage induced in the water by other nearby electric or EM fields. For example, if you move a positive charge up next to salt water, the ions in the salt water will rearrange a bit in response to it and set up a sort of mirror charge in the water (which is true of any conductor and is a common math problem in physics).

2. If that electric field outside the water is varying with time, then the ions in the water will respond to those changes with additional movement, causing what might be called a current in the water.

3. I have never seen any strong evidence that such a movement of ions in the water negatively impacts any reef tank inhabitants. But I cannot prove it does not, and in theory, I'm sure if the field were large enough and strong enough, it could be a problem. I personally do not consider this a substantial risk unless you tank is adjacent to something like a big electrical motor.

4. IF something happens that exposes an electrified conductor in the tank, then the scenario is very different and things can go bad fast. A broken heater, powerhead casing, cord, etc. In that case two things happen.

A. A substantial current can flow in the water, around or even through organisms (probably mostly around in seawater, which is a better conductor than organism tissues due to the higher salt content). That current itself might be a concern in some scenarios, but there's little data on this aspect.

B. At the ends of the current path, meaning at the exposed electrified conductor and wherever it is going, such as a ground) electrochemistry will take place. Two of the biggst potential problems are formation of chlorine (Cl2 from chloride) and dissolution of metals such as copper from the conductor (Cu metal --> Cu+ or Cu++ ions).

 

[Salty_Northerner]

A few folks have noted HLLE effects on fish that went away with a grounding probe. Whether that is real or not, I do not know, but similar effects are not noted for corals that I have seen.

Since we are getting into a detailed discussion, here's my comment on stray voltage from a previous post.

To be honest, there's a lot of commentary around this issue and almost no evidence.

There is also a lot of different opinions of what stray voltage and current even are in a reef tank.

I'll make a few comments...

1. What folks often refer to as "stray" voltage is a voltage induced in the water by other nearby electric or EM fields. For example, if you move a positive charge up next to salt water, the ions in the salt water will rearrange a bit in response to it and set up a sort of mirror charge in the water (which is true of any conductor and is a common math problem in physics).

2. If that electric field outside the water is varying with time, then the ions in the water will respond to those changes with additional movement, causing what might be called a current in the water.

3. I have never seen any strong evidence that such a movement of ions in the water negatively impacts any reef tank inhabitants. But I cannot prove it does not, and in theory, I'm sure if the field were large enough and strong enough, it could be a problem. I personally do not consider this a substantial risk unless you tank is adjacent to something like a big electrical motor.

4. IF something happens that exposes an electrified conductor in the tank, then the scenario is very different and things can go bad fast. A broken heater, powerhead casing, cord, etc. In that case two things happen.

A. A substantial current can flow in the water, around or even through organisms (probably mostly around in seawater, which is a better conductor than organism tissues due to the higher salt content). That current itself might be a concern in some scenarios, but there's little data on this aspect.

B. At the ends of the current path, meaning at the exposed electrified conductor and wherever it is going, such as a ground) electrochemistry will take place. Two of the biggst potential problems are formation of chlorine (Cl2 from chloride) and dissolution of metals such as copper from the conductor (Cu metal --> Cu+ or Cu++ ions).

Hey Randy, just a question here about the op measuring 1.5 volts at times.

What about like our conductivity probes like we would use for testing salinity? Would they put roughly the same voltage across the points of conductivity as in enough to read the 1.5 volts? I'm not entirely sure about conductivity testing devices but is it possible that, that would be where the voltage can also come from or do they not work that way?

 

[Randy Holmes-Farley Verified Community Expert]

Hey Randy, just a question here about the op measuring 1.5 volts at times.

What about like our conductivity probes like we would use for testing salinity? Would they put roughly the same voltage across the points of conductivity as in enough to read the 1.5 volts? I'm not entirely sure about conductivity testing devices but is it possible that, that would be where the voltage can also come from or do they not work that way?

No, for two reasons.

Conductivity probes measure current between 2 or 4 electrodes, not voltage, and conductivity probes use a high frequency AC signal so that one is not actually causing ions to move much between cycles of the signal. We do not want electrochemistry happening at the electrodes, just causing the ions to wobble a bit and we test the wobble (they move more than a wobble might suggest, but the point is very little movement is desired).

Conductivity (electrolytic) - Wikipedia

en.wikipedia.org

"Typical frequencies used are in the range 1–3 kHz."

 

[Salty_Northerner]

Thank you, I was curious how the conductivity on these testers/probes worked. That wiki read was a good read for sure.

 

[jda]

This is just anecdotal at my house, but you need to feel the voltage for it to hurt acropora. I had some acros die off in a frag tank when the skimmer pump was putting out electricity. I could not feel it in the tank, but with the hand in the sump, it gave you a little jump. Instantly started to heal when I replaced the pump.

 

[H@rry]

Just to follow up, I do have GFCI outlets with a ground probe in the sump. I measured the voltage with my meter set on 40V AC, ground probe to the ground in an extension cord plugged into the same AC outlet as the tank equipment, and positive probe in the tank water.

Even before I put the positive probe in the water I could get just a minor momentary voltage "jump" or "jiggle" on the meter. Could "induced voltage" from the PMW circuits of the LEDs cause this? What was more interesting, I unplugged everything from the wall outlets; pumps, powerheads, heaters, lights, controller, etc. and still got less than a volt reading. Almost like a battery or capacitor effect where voltage was stored in the water.

 

[Randy Holmes-Farley Verified Community Expert]

Just to follow up, I do have GFCI outlets with a ground probe in the sump. I measured the voltage with my meter set on 40V AC, ground probe to the ground in an extension cord plugged into the same AC outlet as the tank equipment, and positive probe in the tank water.

Even before I put the positive probe in the water I could get just a minor momentary voltage "jump" or "jiggle" on the meter. Could "induced voltage" from the PMW circuits of the LEDs cause this? What was more interesting, I unplugged everything from the wall outlets; pumps, powerheads, heaters, lights, controller, etc. and still got less than a volt reading. Almost like a battery or capacitor effect where voltage was stored in the water.

Any voltage you measure without tripping a GFCI in a grounded tank is likely induced, not direct flow of electrons.