Originally Posted by Delapool
That is sad news
Water changes as standard recommendation to freshen water up. I assume here the water used for changes is fine (sometimes it seems water companies add things).
Also products like seachem prime / API ammo lock will detoxify ammonia for 24 to 48hrs. Prime will also detoxify nitrites however a small pinch of aquarium salt will also help prevent brown blood disease from the nitrites.
Would you have the readings, including ph? The link below will give some idea of how toxic your ammonia is so we can understand if it is just the ammonia which is a problem.
A bacterial infection is the only thing I can think of (apart from somewhere in water chemistry) that can wipe out fish quickly. I'm sure these have been thought of but some thoughts.
The water here is fine apart from being a ph of around 7.6, other that, no issues with it.
I've been actively using API aquarium salt after water changes to help drop the nitrite levels but it isn't helping as much as I would have liked it to be doing.
My levels as of last night at 8pm GMT are as follows: pH - 8.2 (working on this at the minute, the increase is due to fish death and an issue when my fiancée over fed them) ammonia - 0 ppm
(my tanks cycles ammonia very quickly) nitrite - 1.0/2.0ppm (like I said this is the area of concern but I'm trying to halve this with water changes, aquarium salt, live plants and a backup air pump) nitrate - 0.0/5.00ppm (it jumped slightly the other day until another fish died and it level back out to 0 again, was hopeful my nitrate was going to pick up and lower my nitrite.
I have asked around and the only conclusion various pet stores have come to is that it was neurological and the consequent deaths were due to the water parameters changing.