I have a buenos aires tetra that has developed what seems to be a case of fin rot, but I don't know if that's what it really is or not. The other day I came home and one of the four that I had was dead, for no apparent reason. So I checked the ammonia level in my tank, and it was around 3.0. I couldn't think of a reason for it to be this high, as this tank has been running for over a year and is well past the cycle stage, but it was. Is it possible that a dead fish could push the ammonia that high, or is there some other possible cause? The next day, I come home and find a second buenos aires is missing. I find that it is lodged behind a rock and it looks like it has some kind of white growth on it's back. I figured that it was dying and had been pushed behind the rock by the current from the filter. However, once I moved the rock to get it out, it swims out like it's fine. I looked at it a little more and couldn't really decide if the white stuff was some kind of growth or missing scales from where this fish got lodged behind the rock. So yesterday, it looked about the same, but today it looks a LOT worse. The condition seems to have taken over the back half of the fish and the top half of it's tail fin looks badly rotted. What is the problem, and how can I or should I treat it? Should I treat the whole tank or quarantine the fish and treat it seperately. None of the other fish show any signs of trouble. After I found the first dead fish I did a water change, and below are the results from when I tested the water this morning. What gives?
Ammonia- .25
Nitrate-80
Nitrite-0
GH-300
KH-120
pH- 8.4
Ammonia- .25
Nitrate-80
Nitrite-0
GH-300
KH-120
pH- 8.4
