Lost all but bichirs overnight

[Joshua75]

Went for a trip overnight. Came home to find all my fish dead except my bichirs, and the air pump had failed. I understand bichirs can breathe air, water conditions were absolutely perfect when I left. I had literally just done a water change. I used treated water and did it same as usual. Don't know how long the air pump was out but it can't have been more than 20 - 30 hours. Tank was cloudy and fish were already decomposing. But the contractor working on my house says they looked fine when he left, 21 hours before I came home. Granted he probably wouldn't have noticed the air pump being out or the fish being ill.

Wondering what the hell happened but all signs point to the pump. Looking for advice before moving the bichirs back in. I changed out all the water, cycled it with fresh water by running a hose in and the pump out for some time until water was clear. I did this with the filters off, then added dechlorinator and mixed up the water so it wouldn't kill the colony, then turned the filters back on.

Should I cycle the whole tank again? Should I be looking for another culprit? Was there enough time to explain the fish dying and decomposing in 21 hours. Bichirs seem fine other than cramped in a 10 gallon while I fix this mess. There is a store that will baby sit the bichir if I need longer. I was hoping I could put them back in once the temperature comes back so long as the ammonia and nitrate/nitrite levels check out. So far, since cleaning and refilling, everything is testing good. I couldn't bear losing the bichirs too so I need to do this right.

Thanks or any advice.

Tank is 120 gallon, all fish were small (2-3 inches) still except the bichir.
2 cascade 1000 canister filters.
Was at 78 degrees.
I lost 3 clown loaches, 2.5 inches, 2 acara, 3 inches, 1 pike cichlid 4 inches, 1 fire eel 12 inches.

Surviving,
1 ornate bichir, 14 inches.
1 speckled bichir, 10 inches.

 

[Coryloach]

Sorry for your loss, it must have been a terrible sight to come back to.

Do you mean the air pump was off but the filters were running? It makes no sense to have such a disaster because of an air pump?
A tank going low on oxygen is very possible, but it involves overstocked tanks and very dirty filters and the air pump stopping tipping it off.

But the contractor working on my house says they looked fine when he left,

Just wondering, what was the contractor doing? Any possible chemical contamination?

 

[Joshua75]

Sorry for your loss, it must have been a terrible sight to come back to.

Do you mean the air pump was off but the filters were running? It makes no sense to have such a disaster because of an air pump?
A tank going low on oxygen is very possible, but it involves overstocked tanks and very dirty filters and the air pump stopping tipping it off.



Just wondering, what was the contractor doing? Any possible chemical contamination?

He was working in the garage but came in to use the restroom. Shouldn't be any contamination unless he did it on purpose.

 

[Joshua75]

Sorry for your loss, it must have been a terrible sight to come back to.

Do you mean the air pump was off but the filters were running? It makes no sense to have such a disaster because of an air pump?
A tank going low on oxygen is very possible, but it involves overstocked tanks and very dirty filters and the air pump stopping tipping it off.



Just wondering, what was the contractor doing? Any possible chemical contamination?

Sorry, just saw the first part of your comment. Yeah the air pump was plugged in to a separate outlet from the filters. It seems weird to me that it happened so fast. It was horrible. I loved those fish. I figure it had to already be off when the contractor left. My other tank is fine. Knock on wood. At first I thought the contractor had done something. But the bichir both can breathe off the surface so that would explain them surviving. And the air pump was the only thing off when I came back. Temp was fine. Just a cloud and a bunch of bodies.

 

[twentyleagues]

That air pump isnt putting o2 in the water by being on. Its allowing some small amount of surface aggitation to allow gas exchange. The air pump being off didnt cause this.
How long has the tank been set up?
Does the output from your canister disturb the surface at all? It should if not.
How did the bodies look? Intact? Or missing pieces?
How often do you clean the filters?
How were the fish after the waterchange?
Sorry for the questions I know this is hard, but that air pump off for that short time imho is not/could not be the cause.

 

[Joshua75]

That air pump isnt putting o2 in the water by being on. Its allowing some small amount of surface aggitation to allow gas exchange. The air pump being off didnt cause this.
How long has the tank been set up?
Does the output from your canister disturb the surface at all? It should if not.
How did the bodies look? Intact? Or missing pieces?
How often do you clean the filters?
How were the fish after the waterchange?
Sorry for the questions I know this is hard, but that air pump off for that short time imho is not/could not be the cause.

The tank has been set up for a little less than a year. Cleaned one filter about two months ago, set up the second one about a month ago. Had two HOB's previously. There is surface agitation, the whole surface is constantly moving, albeit not super fast. I could raise the spray bars up to increase agitation. Bodies were intact. Water was cloudy with lots of particles in it though. Fish were acting normal after the water change. It was a 30% water change temp matched. They may have been without oxygen for as long as a 33 hours but no longer.

 

[TheReefer]

That air pump isnt putting o2 in the water by being on. Its allowing some small amount of surface aggitation to allow gas exchange. The air pump being off didnt cause this.
How long has the tank been set up?
Does the output from your canister disturb the surface at all? It should if not.
How did the bodies look? Intact? Or missing pieces?
How often do you clean the filters?
How were the fish after the waterchange?
Sorry for the questions I know this is hard, but that air pump off for that short time imho is not/could not be the cause.

especially because bichirs can breathe air

 

[twentyleagues]

The tank has been set up for a little less than a year. Cleaned one filter about two months ago, set up the second one about a month ago. Had two HOB's previously. There is surface agitation, the whole surface is constantly moving, albeit not super fast. I could raise the spray bars up to increase agitation. Bodies were intact. Water was cloudy with lots of particles in it though. Fish were acting normal after the water change. It was a 30% water change temp matched. They may have been without oxygen for as long as a 33 hours but no longer.

Not if there is surface aggitation. Yes let the water returning to the tank drop to the surface of the water in the tank where possible. This will help with oxygenation. I still say it wasnt the air pump. What happened to the flag cichlid and the ghost knife they still around?
Didnt see them on the list of dead.

 

[Joshua75]

Not if there is surface aggitation. Yes let the water returning to the tank drop to the surface of the water in the tank where possible. This will help with oxygenation. I still say it wasnt the air pump. What happened to the flag cichlid and the ghost knife they still around?
Didnt see them on the list of dead.

I had rehomed them. Luckily for them.

 

[Rocksor]

Not if there is surface aggitation. Yes let the water returning to the tank drop to the surface of the water in the tank where possible. This will help with oxygenation. I still say it wasnt the air pump. What happened to the flag cichlid and the ghost knife they still around?

Maybe there was a power outage for an extended period of time, and when it finally came back on, the air pump couldn't handle the surge of power.