Julii Cories Sudden Illness/death - What's Wrong?

[erica234]

One of my Julii cory's was breathing quite rapidly last night, I came down this morning & his breathing was really laboured and he was just sort of drifting with the water and kept falling on his side (needless to say he was dead within about half an hour). Problem is another Julii has started breathing rapidly and I'm concerned that it will be the same thing.

All water parameters are fine (checked last night and again this morning - also did a 25% water change just to make sure) and I've not added any new fish or plants to the tank recently. Any idea what it might be? Could it be a parasite or something?

Also I have recently begun using some freeze dried blood worms as an addition to the pellets (only once a week) and used some algae waffers for the first time on Saturday.

Other tank mates: Glowlight tetras and 1 x horned nerite snail.

Any help would be really appreciated! Tried calling local store and they were useless!

Additional Details Ammonia: was between 0 and 0.25 (was practically 0 but had a few hints of green when testing. Think this may have been due to a few leaves on one of my vallisneria having died - have since removed them)

Nitrite: 0

Nitrate: 5.0-10.0 (was advised that anything below 20 was okay)

water temperature: 24

Julii that died had no obvious external symptoms aside from breathing problems.

 

[greenmumma141]

How is the water flow in your tank? do you have an airstone or anything to create oxygen? Cories need a lot of oxygen in the water, some species being more sensitive to it than others. While the labored breathing points to ammonia, and anything over 0 ppm isnt good, I still don't think under .25 would kill them, unless there isn't enough oxygen in the water. 

 

[eaglesaquarium]

What's the pH?   Ammonia turns to ammonium (non-toxic) at lower pH, but it is toxic at higher pH, and cories generally prefer lower pH, so it could be a double whammy...
 
 
Also, ammonia poisoning also enables the fish to be more susceptible to secondary infections...