Massive overnight die off in African Cichlid tank

[BobbyZee]

This morning I found ~15 out of ~20 cichlids dead in a 125 G tank. All ate well as always during yesterday’s feeding. The tank has a working cycled FX6 filter. This group has been together for about three years. No new fish have been added other than a few bred in the tank that managed to escape being eaten. I don’t keep live plants. Nothing whatsoever new was added. There are no visible signs of disease. Their air pumps were on & the temperature is as always, around 75F. I did a 50% water change on Saturday, three days ago. I cannot say for 100% that I treated the water with API tapwater conditioner, but I seldom, if ever, forget and can’t accurately say if this is a possibility. If so, would it have caused this massive die off three days after the water change? Any theories?
I am heartbroken.
The ammonia is high at 1.0 ppm. It has never been so high & I suspect the deaths spiked it. Nitrites at 0. Nitrates higher than usual at 40 pp.

 

[Ichthys]

Aerosol sprays in the room? Power outage that came back on?

If it had happened straight after the water change there would be more guesses. Three days is a bit odd.

The ammonia could be post-die off, but would it have spiked this soon?

Any unusual behaviour yesterday?

Could only one have died, and gone unnoticed, and caused the ammonia spike that killed the others?

 

[Colin_T]

A water change 3 days ago shouldn't kill a lot of fish today so it's unlikely the water change caused this.

The high ammonia level could be from the dead fish.

Because no new fish have been added in a while and nothing different has happened to the tank, the most likely cause is a power failure. The filters go off during the night and there may or may not have been an ammonia reading before this happened. If you fed the fish shortly before lights out there might have been ammonia in the water and if the filter stopped shortly after that the ammonia levels would have remained, poisoning the fish. In the high pH of water for Rift Lake tanks, any ammonia is lethal and the higher the ammonia, the more toxic it becomes. When a fish dies it releases more ammonia and that makes the levels in the aquarium higher and you get a wipe out. We had it happen a number of times in marine tanks at one of the shops I worked at. The circuit breaker would trip on the marine displays and they would go without power for 4-8 hours and the fish would all be dead in the morning.

At this stage do a big (75-90%) water change and gravel clean the substrate. Clean the filter too. Wash filter media/ materials in a bucket of tank water before doing the water change. Re-use the filter media. See how the remaining fish go over the next few weeks.

There will probably be a power struggle between remaining males and there could be fights due to various fish missing and others re-establishing territories.

 

[gwand]

A water change 3 days ago shouldn't kill a lot of fish today so it's unlikely the water change caused this.

The high ammonia level could be from the dead fish.

Because no new fish have been added in a while and nothing different has happened to the tank, the most likely cause is a power failure. The filters go off during the night and there may or may not have been an ammonia reading before this happened. If you fed the fish shortly before lights out there might have been ammonia in the water and if the filter stopped shortly after that the ammonia levels would have remained, poisoning the fish. In the high pH of water for Rift Lake tanks, any ammonia is lethal and the higher the ammonia, the more toxic it becomes. When a fish dies it releases more ammonia and that makes the levels in the aquarium higher and you get a wipe out. We had it happen a number of times in marine tanks at one of the shops I worked at. The circuit breaker would trip on the marine displays and they would go without power for 4-8 hours and the fish would all be dead in the morning.

At this stage do a big (75-90%) water change and gravel clean the substrate. Clean the filter too. Wash filter media/ materials in a bucket of tank water before doing the water change. Re-use the filter media. See how the remaining fish go over the next few weeks.

There will probably be a power struggle between remaining males and there could be fights due to various fish missing and others re-establishing territories.

Colin, Sorry for interrupting the thread. But why wash filter in tank water?

 

[Magnum Man]

I never wash the filters in actual tank water... but I do wash them in "tank safe" water, & refill them with actual tank water... I'm not @Colin_T ... obviously, but I always thought the idea was not to wash the filters in tap water that may contain chlorine, which could kill the beneficial bacteria in the filter media

 

[BobbyZee]

Aerosol sprays in the room? Power outage that came back on?

If it had happened straight after the water change there would be more guesses. Three days is a bit odd.

The ammonia could be post-die off, but would it have spiked this soon?

Any unusual behaviour yesterday?

Could only one have died, and gone unnoticed, and caused the ammonia spike that killed the others?

No sprays in this room that has 7 other tanks, all doing well.
No unusual behavior.
I don’t know exactly how long it would take the deaths of several large fish to spike the ammonia.
Extremely unlikely one died unnoticed and caused a spike that killed so many others.
I don’t even know if the an ammonia spike for no apparent reason caused this tragedy.

 

[BobbyZee]

A water change 3 days ago shouldn't kill a lot of fish today so it's unlikely the water change caused this.

The high ammonia level could be from the dead fish.

Because no new fish have been added in a while and nothing different has happened to the tank, the most likely cause is a power failure. The filters go off during the night and there may or may not have been an ammonia reading before this happened. If you fed the fish shortly before lights out there might have been ammonia in the water and if the filter stopped shortly after that the ammonia levels would have remained, poisoning the fish. In the high pH of water for Rift Lake tanks, any ammonia is lethal and the higher the ammonia, the more toxic it becomes. When a fish dies it releases more ammonia and that makes the levels in the aquarium higher and you get a wipe out. We had it happen a number of times in marine tanks at one of the shops I worked at. The circuit breaker would trip on the marine displays and they would go without power for 4-8 hours and the fish would all be dead in the morning.

At this stage do a big (75-90%) water change and gravel clean the substrate. Clean the filter too. Wash filter media/ materials in a bucket of tank water before doing the water change. Re-use the filter media. See how the remaining fish go over the next few weeks.

There will probably be a power struggle between remaining males and there could be fights due to various fish missing and others re-establishing territories.

When the power goes down here, even for a second or two, all the electric clocks, including on the microwave & stove, flicker & must be reset.

I did a 75% water change. You’re saying clean the FX6 too?

I have a DIY water exchange system made from 3/4” hose & PVC pipe.
I did the 75% water change with this. Am I at risk of passing a pathogen to the other tanks from the exchange set up?

 

[Colin_T]

Colin, Sorry for interrupting the thread. But why wash filter in tank water?

Filter media/ materials should be washed/ cleaned in tank water preferably (or dechlorinated water) so you don't kill the beneficial filter bacteria. They add chlorine/ chloramine to tap water specifically to kill bacteria and other microscopic organisms, this includes beneficial filter bacteria. Some bacteria might survive being washed under tap water but most don't (it depends on how much time they are exposed to chlorinated water and how well you wash the media). But it's safer to simply wash the media in a bucket of aquarium water so you don't lose any beneficial bacteria and don't get ammonia spikes after cleaning the filter.

the filter case and impeller assembly can be washed under tap water because they don't house the beneficial filter bacteria.

 

[BobbyZee]

I never wash the filters in actual tank water... but I do wash them in "tank safe" water, & refill them with actual tank water... Not @Colin_T ... obviously, but I always thought the idea was not to wash the filters in tap water that may contain chlorine, which could kill the beneficial bacteria in the filter media

I always use API tap water conditioner to clean filters

 

[BobbyZee]

Filter media/ materials should be washed/ cleaned in tank water preferably (or dechlorinated water) so you don't kill the beneficial filter bacteria. They add chlorine/ chloramine to tap water specifically to kill bacteria and other microscopic organisms, this includes beneficial filter bacteria. Some bacteria might survive being washed under tap water but most don't (it depends on how much time they are exposed to chlorinated water and how well you wash the media). But it's safer to simply wash the media in a bucket of aquarium water so you don't lose any beneficial bacteria and don't get ammonia spikes after cleaning the filter.

the filter case and impeller assembly can be washed under tap water because they don't house the beneficial filter bacteria.

You don’t think conditioned tap water is just as effective for cleaning filter media?

 

[Colin_T]

When the power goes down here, even for a second or two, all the electric clocks, including on the microwave & stove, flicker & must be reset.

I did a 75% water change. You’re saying clean the FX6 too?

I have a DIY water exchange system made from 3/4” hose & PVC pipe.
I did the 75% water change with this. Am I at risk of passing a pathogen to the other tanks from the exchange set up?

Maybe a filter plug came loose, or the filter is blocked and needs a clean. Maybe a circuit breaker tripped on that room, but entire tanks of fish don't just wipe out overnight from disease unless there is a well established disease beforehand.

I would clean the FX filter too if it hasn't been done in the last 2 weeks.

We don't know if a disease caused this. Pictures (if you have any) of the dead and remaining live fish might provide more information but entire tanks of fish don't just die overnight from a disease. Poor water quality, poisoning or lack of oxygen are the most common causes for tanks wiping out overnight.

Unless used tank water passes from one tank to another, there is not much chance of disease spreading to other tanks, assuming this was a disease, and I doubt it was. I could be wrong but it's unlikely to be a disease.

 

[Colin_T]

You don’t think conditioned tap water is just as effective for cleaning filter media?

Nope. The filter bacteria live in the aquarium water, which has a certain chemistry (GH, KH & pH), temperature, and is free of chlorine/ chloramine. Tap water can be different to these and everything that is different can affect the bacteria. Your water company might have done work on the pipes recently and added extra chlorine/ chloramine to make sure nothing lives in the water and you could use that heavily chlorinated water on the filter and kill the bacteria. Major temperature changes can affect the bacteria. If the filter media is exposed to sunlight (even for a few minutes), it can affect the bacteria.

 

[Magnum Man]

could you have some stray voltage from a heater, light, or filter motor, wave maker, or similar... it seems pretty traumatic to lose that many fish overnight, however, yes, ammonia could kill that fast...

 

[BobbyZee]

Maybe a filter plug came loose, or the filter is blocked and needs a clean. Maybe a circuit breaker tripped on that room, but entire tanks of fish don't just wipe out overnight from disease unless there is a well established disease beforehand.

I would clean the FX filter too if it hasn't been done in the last 2 weeks.

We don't know if a disease caused this. Pictures (if you have any) of the dead and remaining live fish might provide more information but entire tanks of fish don't just die overnight from a disease. Poor water quality, poisoning or lack of oxygen are the most common causes for tanks wiping out overnight.

Unless used tank water passes from one tank to another, there is not much chance of disease spreading to other tanks, assuming this was a disease, and I doubt it was. I could be wrong but it's unlikely to be a disease.

Actually good news that this is unlikely to be contagious.

No way I will dig the bodies of my dead pets from the outside bin. Their appearance now is unlikely to resemble what it did six hours ago anyway. It will bring me more sorrows to see them again. As to their survivors, they appear perfectly normal and I do not care to photograph them either. I seriously doubt you could ascertain anything from what appear to be healthy, active & eating fish.

I did increase the oxygen in the tank by replacing both smaller air stones with quite large ones that must weigh close to a pound each, or at least it seems that way.

I did clean the FX6, which actually didn’t look bad given a recent cleaning.

I can’t imagine what would have poisoned them given that nine other tanks of fish were fed the same diet. As to water quality, that is something I’ve never been guilty of. Hence, the 3/4 inch hose system that pumps appropriately heated water from a bin in the tub, speedily. A simple task I have never neglected. Nonetheless, they are dead and I don’t know why and I will continue to search for answers. I’ll let you know if I come up with anything.

I really appreciate your suggestion to clean the filter and up the O2.
Thank you, Colin T. I’m actually a Facebook person, but was directed to this forum because of you.

 

[FishyD]

Already mentioned, but if you are certain a toxin like an aerosol could not have entered, then a fish dying unnoticed seems like the next best guess. I am pretty sure a chlorine problem would have shown some noticeable symptoms day one, as it is obviously a strong toxin.