Grounding Probes: Gadget or not?

[JT101]

My AP24 has been established since June 2007. On a whim, just today, I dropped one lead of a DVM into the tank, set the DVM to AC volts, then touched the other lead to the ground pin of the closest AC outlet. I was pretty astonished to read a voltage of 13.85VAC!!! I have no idea how long it has been like this.

Now, I understand that I can buy one of those "grounding probes" that will essentially "ground" the tank water by reducing the voltage drop between the water and earth ground to essentially 0VAC (or the lowest voltage drop possible given the gauge of the wire and the current flowing through it). Before I do that: What benefits will I see? Is there even a benefit to realize?

The reason I doubt benefits from using grounding probes is because of the old "bird on a wire" analogy. Say a bird is flying along and decides to land on a 100,000V high-tension wire. They, in fact, do this all the time - yet they never die (or are even slightly injured) as a result. Why? Well, it's because since they are not touching anything else before or after alighting on the cable, their body charges-up from a relatively low-voltage charge to whatever voltage the cable is carrying (100kV in this case). As a result, there is no voltage drop from the body of the bird to any other entity, which results in no current flow, which results in no change in the state of the animal. Now, if they happen to touch a grounded object while on the wire, their bodies will see a 100kV gradient, which will result in the full voltage drop across the bird, which, in the case of the super-high current being carried by high-tension wires, will result in instant "bird flambe"!

Ever see a helicopter wire repair crew? The heli hovers near a wire that is at full power and a repairman actually steps outside and works on the wire, and can do this with bare hands. This is because the same phenomenon is at work here: The entire helicopter and all of its inhabitants simply "float" at 100kV. As long as the helicopter stays aloft and the rotor blades never get close enough to the tower's superstructure to arc over, everyone will be fine.

The key here is: No current flow = no physical effect.

The same should hold true for reef tank inhabitants. In this case, we can just replace air with water, and charge up the inhabitants to 13.85VAC. As long as they never touch a grounded surface they should be fine. Now, if you drop a grounding probe in the water, the same thing applies, and, since there is a voltage present in my case, that is proof positive that the entire tank is "floating", so the fish/corals/snails can never come in contact with a grounded object (said differently, IF there already WAS a grounded object in my tank then there wouldn't be any "stray" voltage to begin with). The water's charge (voltage elevation, really) drops to 0VAC, and so does the fish's and all other inhabitants. What really changed? Should we expect the fish to feel/act any differently before or after the event?

I would appreciate anyone offering some deeper insight into the benefits of tank grounding probes.

Thanks
John

 

[Dentoid]

My understanding is that it affects the fishes lateral line and has been implicated in causing head and lateral line erosion) HLLE in some species. I can not confirm or deny this, but it makes since as the lateral line is a sense organ that detects movement, vibration and electrical changes in their environment.

 

[JT101]

My understanding is that it affects the fishes lateral line and has been implicated in causing head and lateral line erosion) HLLE in some species. I can not confirm or deny this, but it makes since as the lateral line is a sense organ that detects movement, vibration and electrical changes in their environment.

Hi Dentoid,

Thanks for the reply. However, I still don't understand how there can be an effect. The lateral line works by detecting a delta (change) between it and its surrounding environment. If the fish was at, say, a 0V "charge" (for lack of a better term) then any change picked up along the lateral lines would be due to changes. Now, let's elevate the entire tank's water environment (relative to earth ground) to 13.85VAC. The fish would "charge" up to the same level. Net result? Zero voltage drop between the fish's tissues and its watery environment. Any changes between the fish and the water would still be picked up. In other words, say that the fish is at 0V and the water is at 0V and a 0.01V change is detected between the fish's lateral line and the water. The line has done its job. Now replace those numbers: The fish is at 13.85VAC, the water is at 13.85VAC, and there is a 0.01 change detected. There should be no difference in how the lateral line works in this case. We could, in theory, extend this line of thinking out to much higher voltages but of course there would be a practical working limit that would be dependent upon the insulative characteristics of the tankstand and what surface it is sitting upon etc.

Again, sorry for making a mountain out of what may really be a very small molehill, but I don't understand the benefits of a grounding probe, because the math doesn't make any sense when you look at it from an electrical POV...

Thanks
John

 

[Dentoid]

I have seen studies where sharks are deflected and manipulated by electrical charges artificially placed in their environment. I don't know the science behind it all or what has been proven in both shark physiology or tropical fish physiology.

It's an interesting subject that I'm sure you will find a lot about on the internet.

 

[JT101]

I have seen studies where sharks are deflected and manipulated by electrical charges artificially placed in their environment. I don't know the science behind it all or what has been proven in both shark physiology or tropical fish physiology.

It's an interesting subject that I'm sure you will find a lot about on the internet.

Thanks Scott. I guess this is something I'm going to have to research a little.

In the meantime, I will be getting a probe, if for no other reason than I am VERY curious as to what would happen. I cannot imagine it doing any harm, but if it makes my tank look even better then I will be even more intrigued to study this subject even further!

Thanks again.
John

 

[Dragonne]

I have a thought on this, as I've been doing the same debate for about a year now. If there is an electrical current level in the water, and it does not ground (all water touching glass, an insulator) there is no circuit completion which shouldn't harm the inhabitants of that water, correct? Here's why I came up with this.

Last year I had a pump seal go bad in my pond which caused discharge into the water. It's a rubber lined pond, causing no discharge. I didn't even know it was happening until my wife (barefoot) reached in to pull out a leaf on the water and got a shock. I told her she was crazy as I did the same thing and didn't feel anything (wearing sneakers). Well, a few days later I was kneeling and reaching for a leaf and got the same shock (wearing shorts, knees were grounded). The fish showed no adverse affects from the constant ungrounded current at all, and I don't even know how long it was like this. I did some experiments and found that the fish would twitch the instant the water was grounded. This leads me to believe that grounding the water may cause more problems than leaving it as is.

Back to the marine tank situation. salt water has a natural current at all times due to the nature of having salts present. Granted, it's likey very small, but it's there, and that's the electrical baseline that fish use to detect the difference in the electromagnetic field of other living creatures (lateral line reference). Noting that the oceans are grounded by their contact with earth and don't likely have any exposed large source of electrical current in them, it is different than our enclosed systems. Also, lightning strikes on water don't seem to harm the fish in that water (at least not that I've heard/read about). This is where I always end up, stuck again in a pile of contradictory semi-evidence.

So, I go back to the basic thought. Ungrounded contact with electricity has minimal effect on biological organisms. Grounded contact can kill (it's called being electrocuted people). I'm thinking that completing the circuit to ground would in fact be detrimental to the inhabitants of the water through which the current passes, no? I've done a bit of research over the past few months and all I find are statements by the retailers of grounding probes that claim they are beneficial by removing stray current or general statements from non-retailers about it being a good thing to ground tanks/ponds... but I still have no hard facts as to why.

Grounding probes are not cheap (relatively for the purpose). Probably because of the materials needed to be used to prevent copper and other heavy metals leeching into the tank and avoid corrosion. Really, one end of a simple conductive wire in the water and the other end in the ground port on a standard socket will do the trick (but will corrode and degrade over time, hence the expense of commercial products to prevent this, and copper is BAAAD for a reef tank). Anyway, my point is the reasons why to put out the expense to have/use a ground probe are not readily apparent due to empirical contradictory evidence, and even contradictory anecdotal evidence.