It is defenitely a chemical. I once had this happen on one of my tanks. The fish would lose their appetite, they swim weirdly, and then they die. For me the whole prosses took less than half an hour. I lost well over 700 dollars worth of stingrays, pbass, and aros. It started when I was re-filling the tank after a 90% water change (I now know that was way too much). When I was adding the water I notice my aro was swimming weirdly and one of my rays was swimming extremely close to the top. I didn't think much about it. 30 minutes later I go to check on everything and all of the fish are either dead or swimming weirdly. An hour later everything was dead except for 1 fish. I put it in a large tupperwear container with a filter and the water from the tank. The next morning it was dead.
The way I fixed was by draining the entire tank and taking evreything out. I threw away all of the used filter media. Then I put everything in the tank and filled the tank with net soak. After 48 hours of soaking I put everything back, filled the tank with water from a different tank, and threw in some used media. The tank is now up and running and I havn't had a major problem like that sinse.
The only thing I can think of is a chemical. The bathroom nextoor was being re-done so I assumed that caused it. Good luck with curing it.
The way I fixed was by draining the entire tank and taking evreything out. I threw away all of the used filter media. Then I put everything in the tank and filled the tank with net soak. After 48 hours of soaking I put everything back, filled the tank with water from a different tank, and threw in some used media. The tank is now up and running and I havn't had a major problem like that sinse.
The only thing I can think of is a chemical. The bathroom nextoor was being re-done so I assumed that caused it. Good luck with curing it.
