Peppered Cories Dying

[Gix]

Howdy all,

I have a 30 US gallon tank, which originally only had 6 harlequin rasboras and a marbled gourami in it. The fish had all been there for the better part of a year and have had no problems, and I have kept the gourami in one tank or another for at least two years.

I got 6 small peppered cory cats on Sunday (06/14, four days ago) and acclimated them to the new tank, and they seemed fine. The next day, my friend, who was at my apartment at the time, called me to say that one cory is dead and others look like they are breathing rapidly. My friend does not know much about fishkeeping, but I got her to siphon out some water so that the current would be less (it is not very strong as it is, but probably strong enough to keep the cories from easily gulping air at the surface) in case it was an oxygen issue. When I got back from work, a total of two cories were dead and another was close, and the other three looked 100% fine. The dead fish had reddened gills, and the one that looked ill was indeed breathing rapidly. The ill one died that day also.

I checked water parameters: ammonia and nitrite 0, nitrate 5-10, pH 6.8-ish. Normal for this tank.

Tuesday and Wednesday passed without incident. The three remaining cories ate well and looked healthy. On Wednesday night (06/17, yesterday), I decided to raise the level of the tank a little bit, and added between 1 and 1.5 gallons of treated water that had sat out since my previous water change. When I wake up today, I see that one cory is dead!

My only assumption is that there is something in the water that I am adding...I had changed the water (about 1/5th only) the day before getting the cories also. Does anyone know what could be going on?? I am stumped!

Thanks for any and all help and suggestions,
Michael

 

[WILDER]

Is there plenty of aeration.

Red inflamed gills can be bad water quality, bacterial gill rot, gill flukes.

Anys igns of flicking and rubbing or excess mucas.
Do the corys swim in a jerky moment.
If no signs of the above I would maybe add a bacterial med to the tank.
Increase aeration.

http/www.thetropicaltank.co.uk/hdgilld.htm

 

[Gix]

Is there plenty of aeration.

Red inflamed gills can be bad water quality, bacterial gill rot, gill flukes.

Anys igns of flicking and rubbing or excess mucas.
Do the corys swim in a jerky moment.
If no signs of the above I would maybe add a bacterial med to the tank.
Increase aeration.

[URL="http/www.thetropicaltank.co.uk/hdgilld.htm"]http/www.thetropicaltank.co.uk/hdgilld.htm[/URL]

There is plenty of aeration; I use a bio-wheel filter and the water level is still at least 1.5 inches below where I usually keep it.
I will treat with some melafix in case it's bacterial. Thanks!

 

[WILDER]

Melafix is only good on cuts and wounds.
Whats your location.

 

[Gix]

Melafix is only good on cuts and wounds.
Whats your location.

I'm in the US

 

[WILDER]

Maracyn–Two
Manufacturer: Mardel
A broad-spectrum antibiotic for internal or external gram negative bacterial infections which can even be absorbed through the skin. Effective treatment of fin and tail rot, popeye, gill disease, dropsy (swollen body, protruding scales), septicemia (bleeding or red streaks on the body), secondary and internal infections. Effective even when fish won't eat.
Active ingredient: Mincycline hydrochlor.

Or maracyn plus.