Dary's tank!

[mr_X]

Originally Posted by rdnelson99

Just like a bird sitting on a power line.

Right. I suppose that's why then, only I did have something happen to corals, but not the fish.
A few years ago I put some live rock into the sump and unknowingly crushed a glass heater. That night i was sitting nearby and saw a blinding light out of the corner of my eye- it was the heater turning on under water. It looked like someone was arc welding in my sump. Smoke was coming out of the water and you could hear a sizzle.
This went on for about 5 seconds until i was able to unplug it. The GFCI did not trip.
No fish were effected, but the corals were. All of the xenia expelled their zooxanthellae and all sps browned out immediately.
The xenia looked at white as paper for about a month.
How do you explain this?

[barterking85]

Not really my place but I would say the corals are grounded I am no expert at all it's just a guess

[mr_X]

But salt water is a conductor. If the corals were grounded, so would the fish be.

[Sqasnatch]

Lots of iron is the water,, doesn't make sense really

[rdnelson99]

The corals are in contact with the rock and/or sand which is in contact with the bottom of the tank. Glass is a good insulator assuming it is clean and dry. In your case, it has salt build up which can conduct the electricity. Current will follow the path of least resistance in proportion. So, something with high resistance will see a little current flow but something with low resistance will see more of the current flow. So bassically, you had current throughout your entire system. Some of it flowed through the corals which affected them negatively. The fish however were surrounded by the water completly, therefore the potention (voltage) on all sides of the fish was equal and no current would flow through them. It is only when you have unequal potential that current will flow.

Think of two buckets connected with a pipe that has a valve in it. If you open the valve but the water is at the same height in each bucket, no water will flow. If however, one bucket has more water than the other, water will flow through the pipe into the other bucket.

[Dary421]

Originally Posted by rdnelson99

The corals are in contact with the rock and/or sand which is in contact with the bottom of the tank. Glass is a good insulator assuming it is clean and dry. In your case, it has salt build up which can conduct the electricity. Current will follow the path of least resistance in proportion. So, something with high resistance will see a little current flow but something with low resistance will see more of the current flow. So bassically, you had current throughout your entire system. Some of it flowed through the corals which affected them negatively. The fish however were surrounded by the water completly, therefore the potention (voltage) on all sides of the fish was equal and no current would flow through them. It is only when you have unequal potential that current will flow.

Think of two buckets connected with a pipe that has a valve in it. If you open the valve but the water is at the same height in each bucket, no water will flow. If however, one bucket has more water than the other, water will flow through the pipe into the other bucket.

So are you saying that dry salt build up outside your tank may actually have caused a ground that could have charged the tank and effected the corals,... If this was the case then if a fish touched a rock/ coral or the side of the tank wouldn't it get a shock also???

[mr_X]

Yeah....I had an algae blenny in the tank too that was unaffected. the odds of him swimming the entire time the tank was shocked are slim. And what about shrimp and other inverts? Nothing was harmed but the corals.

[Dary421]

Originally Posted by mr_X

Yeah....I had an algae blenny in the tank too that was unaffected. the odds of him swimming the entire time the tank was shocked are slim. And what about shrimp and other inverts? Nothing was harmed but the corals.

Could it be that possibly corals may have a natural charge about them wether it be positive or slightly negative that may in turn be effected by stray electrical currents? Or maybe their " stinging" venom conducts the stray currents in a adverse way also ?? ... Just tossing that out for thought

[rdnelson99]

Originally Posted by Dary421

So are you saying that dry salt build up outside your tank may actually have caused a ground that could have charged the tank and effected the corals,... If this was the case then if a fish touched a rock/ coral or the side of the tank wouldn't it get a shock also???

Not exactly. The salt build up could have completed the path but not "charged" the tank. But when the heater turned on electricity would flow through all the water. Pure H2O will not conduct but the salt in it will. The current could have flowed through the corals and on to ground through the salt build up in cracks and crevices. But if at that instant the fish were suspended in the water current would not flow through them.

Also to Mr. X I would say change that GFI. They can go bad and if it did not trip it isn't working correctly.

[rdnelson99]

It is possible that corals have a charge but it would be minimal and would not cancel out 120 volts. Some things naturally would tolerate more current than others. In addition, even if the GCI or the breaker failed to trip I would bet that something in the heater burned in two almost instantly. That was the Arc (flash of light) that you saw. That happened almost immediately clearing the fault. A breaker needs time to build up heat before it trips. If the arc cleared the fault not enough heat built up in tiebreaker to trip it. That is why you need a GCi. It works by sensing an imbalance of current. Normally you would see an equal current flowing through the hot wire and the neutral with no current flowing through the ground. In a ground fault (short to ground) some current will flow through the ground. That means the hot and neutral are no longer balanced and the GCI trips. That is why I said "change the GFi" not change the breaker.