This just happened to us a few weeks ago. My husband fed our 11 fish in our tank amorous d 7pm and everything was good. Had purple tang, tomini tang, pair of clowns and some smaller fish. I came home from work at 11pm and checked the tank, I found almost all the fish upside down on the sand some alive but breathing hard, three stuck to the powerhead, and one missing. The purple tang, one clown were dazed but ok. We shut the tank down and started pulling the fish out. We saved the purple tang and clown but all the ones that were breathing hard died soon after we took them out to move to quarantine. We did put the purple and clown in quarantine. All the snails were dead and one of two cleaner shrimp. The crabs, anemones and coral were all fine no signs of stress. No signs of injury, illness or disease on any fish.. and I watch them like a hawk! After we got the fish out we tried to restart up the tank power and found that the return pump was not working at all. So replaced it with back up. We only turned the heater on also. In am we went and bought a new multimeter and found huge amount of electricity in the tank. We also found an alive gobi who was hiding in the sand-doing fine. We changed out the pump, heater and powerhead with all new equipment from emergency trip to LFS. No more electricity. We put our fish back in tank and they are doing fine. My coral looks better than it ever has also. We did water parameters first by the way and everything was ok but some nitrites which I assume came from the massive die off in the tank, also the alkalinity was 22!!!’ We did water change.. even with the alk that high no signs of stress to coral or anemones. The alk is still 13! And coral looks great. Crazy though. I think the electricity changed the alk if that’s possible??? We did water tests two days before and all water parameters were perfect then...
we have two more tanks- a 300 reef and 300 gal fish only. so just for fun we Checked with the multimeter the other tanks and found over 115milamps of electricity in both those tanks too!!! We were using the same brands of equipment in all three tanks. AND we could NOT feel any electricity in the tanks. But we turned off equipment (4) powerhead a in each tank and found two power heads in each tank we putting off electricity. We removed them and no
More electricity!!! Our fish in the fish only tank immediately looked better and started swimming more and brighter colors. Our tangs in the reef had looked a little pale and also immediately changed colors when we removed the powerheads. We have 2 MP40s left in the big tanks and will just use those for now. Thank goodness we have had no more fish loss. No signs of disease, still. I honestly believe we had a power surge from the pump that failed and electrocuted all the fish and snails.
For some reason we didn’t have a grounding probe on the tank that had the power surge or GFI... stupid on our part we have both those protections on the big tanks which is probably why those fish were even alive at that much electricity. We even watched the multimeter go to 0!!!
We now have extra grounding probes in sumps and tanks and GFI stuff too. We will check for stray voltage monthly from now on. We did order five small new fish. But will not add anymore to our small tank since the coral looks so good. My new fish are in quarantine. I ordered from Live Aquaria for the first time.
I wish you the best and sorry for your loss. I hate loosing animals especially for senseless reasons. Just a few days before I lost ours I was commenting to my husband how happy I was with all our fish
Best of luck to you.