Sorry about your loss. I hope you get things on track soon.
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..
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...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.
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.My question is, do fish ever fully recover from nitrite poisoning?
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..