10 Rainbows Died Overnight????

[FSEMTB2]

I had these fish in an established/planted tank for over a year now. I woke up and found 10 had passed overnight. The fish were extremly healthy prior to this.

I did my normal 50-60% water change the evening before. The water was treated and at proper temp. When I looked over the tank the heated was working, powerfilter working, and canister filter working. The sylenoid for the CO2 was shut down, pretty much evry thing looked normal. I did notice that the remaining fish were grasping at the service a lot. But this is a mystery because all filters working and CO2 wasnt getting injected.

Anybody have thoughts on this? How does 10 perfectly healthy fish(rainbows being hardy)pass away?

Ken

 

[norcalg]

I'm sorry for your loss. And my lack of any help but I just lost one in an afternoon. My ballast died, the lights went out for a day and when I got home after a few hours, one of my 9 rainbows was dead. No signs of ill-health prior and no losses since (knock wood). Were any other fish in the tank acting weird? With the gasping, I'd think lack of O2 but then others would be affected as well, wouldn't they?

Again, sorry I'm no help.

~g

 

[rich311k]

It is either lack of O2 or ammonia or nitrite poisoning. Are the remaining fish astill gasping at the top?

I am sorry for the loss.

 

[roka64]

It sounds almost like the temp is too high, not enough O2 in the water or a gill disease. I would look more at the water temp or O2 as the culprits. Do you have a thermometer in the tank? What are the water parameters? pH as well?
Sorry for your losses.

 

[FSEMTB2]

The temp on the tank is a steady 78 degress and the new water that went in the tank was the same. Ammonia or Nitrite spike? Is that possible after a 50% water change? I would of thought after the water change the water would of been at a peak quality. These fish SEEMED to be perfectly healthy, with no signs of stress or disease.

What would make the O2 level drop down to deadly level. Once again this is a planted tank and has been running for a year with out any problems.

I guess these are the things that keep the hobby so interesteing. Trying to figure out nature in a glass box.

 

[src]

I saw something similar with my wife's Congo Tetras a while back. We had been very busy (and out of town a lot) for several weeks, so we hadn't done a water change in a while. Unfortunately, we then performed the normal 70% change without testing the parameters first. ALL of her Congos died within an hour. Oddly, the Columbians and Albino Corys were just fine. We think that the tank had built up a high nitrate load (it was an established tank), and diluting it by 2/3 shocked the fish.

If you do regular water changes on a correctly stocked tank, this shouldn't be a problem, but just in case...

 

[Zagz]

I would think that oxygen dropping or an ammonia or nitrite spike may be the cause. Test your tap water to be safe. I doubt your nitrates built up too high in a planted tank to cause a shock to the fish's system with a water change but anything is possible. I tend to think O2 would be more likely.

 

[FSEMTB2]

Any explanation on why the oxygen level would drop to a point that the fish would die?

 

[JustOneMore20]

Is your CO2 tank empty? If the CO2 was low in the tank, it could have dumped the last of it, if it was on after you did the water change.

Thats very strange to have them all die like that, even after a water change.

Sorry for your losses.