corys swollen gill... help!

[aquatix02]

hi.. i have a problem with my corydoras julii

my corys have been in my 7G zeolite box-filtered quarantine tank for about 10 days. one of them has just recently developed a swollen gill (or something like that) on one side and the red gilles on the other... also it also floats in mid-tank or nearer to the surface (presumably to get more oxygen) at times, at other times it lies motionless at the bottom. my other two corydoras are fine and actively searching for food all over.

does anyone know what the problem may be? could it be a disease? would really appreciate it if someone could help me out!

also... i add amquel approximately once every 3 days and do after I do a 25% water change with a siphon.

thanks!

 

[wetmanNY]

Gill damage is more often the result of gill parasites, either protists or flukes, than it is longterm exposure to gill-damaging toxins: ammonia, nitrites, chloramines etc etc.

By the time the operculum no longer closes, the gill lamellae have permanently swollen ("hyperplasia") and the fish will pump hard to get oxygen.