Mysterious deaths to only one species

[Coryloach]

Sorry about your loss. I hope you get things on track soon.

What makes me think it's not the water quality as I have a couple pairs of G. mirabilis are already showing mating behavior and the altums are growing showing their markings and eating very well.
Edit: added what I feed and tank observations.

I wanted to note that fish do breed in extremely poor water quality. Years ago I had corydoras lay eggs in ammonia that was off the charts and the tank stunk of chemicals. Their fins actually melted overnight but they still laid eggs...

My question is, do fish ever fully recover from nitrite poisoning?

Elevated nitrites can be counteracted with a bit of salt in the water to neutralize the toxicity of nitrite but from what I know, once the damage is done, it is normally permanent. It is impossible to know if the damage is extensive....for now...From my own experience, fish subjected to high levels of either ammonia or nitrite hardly live through the following year, dropping dead from weird alignments, simply due to the fact that their immune system was compromised and not recovered to fight off pathogens naturally occurring in the tank.

It of course depends on how long the exposure was, how good their health was prior to that, , how well they are looked after subsequently. In good water quality post the accident and well maintained tank they should be fine but some of the survivors will be weaker individuals and may not live up to a ripe old age, especially not if subjected to bad water quality again.

I'd personally now stick to more regular large water changes and I'd get my hands on the best quality fish food available such as New Life Spectrum. Think about maintaining exceptional environments for those weak fish for months ahead, in order for them to have the best chance of recovery, rather than parking your slippers because your nitrite test now says zero..

 

[MrsE88]

If you can get your hands on a microscope you could start ruling out parasites and possibly bacteria. Or better yet find what is causing all your loses.
I’m sorry things have gone down hill so fast. I hope you will be able to save some of your stock.

 

[squint]

Consider getting one of these to rule out chlorine (which does cause red gills).

 

[squint]

Wait, you live in Elk Grove, only ~20 miles away from the #1 veterinary school in the world.

They do see fish there as well as perform water testing with laboratory grade equipment.

 

[IronSnake]

Just had another death of a G. mirabilis. The gills are not red but pink towards more white flesh throughout.

 

[squint]

Did you increase the dose of Seachem Safe like I suggested earlier?

 

[IronSnake]

I did increase Seachem Safe to 3x. I’m thinking the damage to their gills were permanent due to the nitrite poisoning. The obvious sign is the ones dying are the ones with mouths open gasping for air, while the few resilient ones don’t even open their mouths to breath. From now on, two test kits for me just in case to avoid bad luck.

 

[squint]

I did increase Seachem Safe to 3x. I’m thinking the damage to their gills were permanent due to the nitrite poisoning. The obvious sign is the ones dying are the ones with mouths open gasping for air, while the few resilient ones don’t even open their mouths to breath. From now on, two test kits for me just in case to avoid bad luck.

Nitrite doesn't damage gills though. It converts hemoglobin to methemoglobin but that's converted back within a few hours after removal to low-nitrite waters or the application of chloride.

 

[Galantspeedz]

i am concerned with the lack of pictures

 

[IronSnake]

Final update on this, sorry for the hiatus as I was simply crushed and angry at myself. Sad news, most of the fish died which I believe was nitrite poisoning. I had to step away and just deal with the total tank wipe eventually as the remaining OGs days are numbered. The only good news is all the fish that I introduced when I caught the faulty nitrite test are thriving and no deaths from that group. I've been testing twice a week and the tank parameters are stable and perfect. I've also managed to get nitrates to almost zero thanks to a mature algae scrubber and I've gone without water changes for a month now. I will let the tank be now that is winter, and re-stock next spring. Thanks for all the support.