Ok. I have so much to say on this and not enough time and hard to write the emotion that goes into it. I had this happen, and have first hand experience...
I had gotten some Anthias and a powder blue tang. Both were eating great and doing great for 2-3 months.
Then suddenly, I found a fish jumped out. Then two fish dead a week later for no reason in the rocks. Then about 5-7 days later my Banghai cardinals were in various states of popeye and died off one by one.
My Powder blue then developed welts all over its body and died another week later. I was testing everything and not overreacting. I did a 30 % water change, monitored basics like salinity, testing with multiple calibrated refractometers. I tested my chemistry. I couldn't figure it out.
3 weeks in I had lost 15 fish all in different ways (350 gallon display). I had never been shocked, I work in my 350 too much an hour or two every week cleaning the glass, doing maintenance on powerheads, you name it. There's always something to do. . . I never felt a shock.
I was at my wits end. I talked to the local fish store owner (salt water store) and asked him what the heck why is everything dying.
His first question was "How are your corals fairing?" I said, you know, now that you ask, I've noticed several corals that were not growing at all now having visible growth in the last month. Several of them noticeably larger. I said that's the confusing part, if it was something in the water, like metal, copper, or other things that are bad for both inverts and fish, wouldn't my snails and corals be dying... Which, yes, the answer usually is yes. Salinity, snails, anemones (of which none of mine were showing any signs of stress.)
He said, have you checked for stray voltage? I said, no, but why would I. My corals would be dying. . . "He said, nope, google electrified cages to rebuild a reef in the 1980s."
I said, "HUH?"
There are many articles out there now on google, showing how we're advancing the use of electricity to help corals grow skeletons faster and easier. However, stray voltage can stress fish significantly.
I told the fish store owner he's crazy. I stick my hands in the tank all the time. I don't feel any shocks. " He gave me a strange look, like how dumb are you?
"Your body needs to be thoroughly grounded in order to feel it."
I don't recommend this, because what I did next could have killed me. But, I stuck my hand in the sump and placed my other hand on something I assumed would be grounded, the metal sides of my furnace / air handler. I think my hair stood up on end. I couldn't believe it.
I still thought maybe, like you, it was a salt sting.. Chemical burn type feeling. But my hair on my neck stood up. My hand vibrated that was in the sump. The hand touching the furnace stung. Almost hurt.
I said o.k. maybe there's truth to this. I used my apex to shut pumps off one at a time. I had a couple corded powerheads, skimmer pump, and two 300 watt heaters that were submerged. So, it would be easy to turn each off one at a time to find the culprit. Sticking my hand in each time to verify if the electricity was gone..
I discovered one of my two 300 watt heaters was leaking electricity. The vibrating stopped. Just to confirm I turned the heater back on and retested and sure enough the sting and electrical charge was there again. I then shut it off and watched my last few remaining fish and my black long nose tang whom had stopped swimming the full length of the tank for some time, now was swimming gleefully the full 6 feet of the tank. I went and turned the heater back on and observed the tank. It seriously went to swimming in small concentric circles.
I turned the heater off. Pulled it out. purchased two new Finnex heaters from the LFS. threw both of the old ones out.
I was able to save one fish. My Black long nose tang. That was going on 3 years ago. It took 4-5 weeks to find the problem. I lost in total 16-17 fish from that incident. Hundreds of dollars down the drain.
Having getting that all in check, I didn't trust there weren't secondary issues like other bacteria, disease, viruses, parasites that the electricity fostered in the fish. I left the tank for 4 -5 months with just the black tang in it. He was lonely in a 350. But, I just was so disgusted with it all I couldn't bring myself to add more fish.
Now, three years later, same tank, same everything except the 2-3 year old heaters now. I have 25 new fish. Many of them going on 2 years old now and healthy. My black long nose tang is going on 7-8 years old.
I can't express how defeated you must feel. I almost gave up. If it wasn't in my wall in the basement, I might have given up.. But, I let it sit, neglected it a few months then restarted it slowly adding a few fish every 2-3 months. And they have all thrived since then.
Electricity does kill fish, it affects their brains, their immune systems, and their ability survive. It however, will help corals to put down new skeletons, causing them to look healthier and grow faster.
I'm very sorry!
