Pale Corydoras

[MissEfish]

Hi, I'm new and posting because I'm worried about my Green Cory cats.

I have a 46g bowfront that I set up about two months ago. The tank is moderatly planted with java fern, amazon swords, and a few other species. I have been stocking the tank by adding a few new fish each week and it is currently home to 5 sunburst platies, 6 zebra danios, 4 green corydoras, and most recently 3 dwarf gourami.

The corys were added just before the new year. Originally there were five but a few days after I bought them one became very pale and lethargic. Instead of hiding in the cave or playing with the others he would lay out in the open, sometimes on his side, and not move. After about three days he died. Everyone else in the tank seemed to be doing ok and the water parameters were normal so I assumed he must have been sick when I purchased him.

This morning, after about 3 weeks with no problems I found one of my remaining corys exhibiting the same symptoms. He has lost most of his color, is laying out in the open, and moves very little.

My water parameters are:

Ammonia 0
Nitrite 0
Nitrate <20
Hardness 75ppm
Chlorine 0
Alkalinity 40-80ppm
pH 6.8

No one else in the tank is behaving strangely and the other 3 corys are playing normally.

Any ideas what the problem might be and what I can do to fix it? I'd like to save this fish if possible, but I also want to prevent the problem from spreading to the rest of them.

 

[WILDER]

Corys are more prone to bacerial infections.
Laying to one side is a symtom of a bacerial infection.
Is the fish bloated, any sores on the body of the fish.
Check the barbels to see if the short and thin.

 

[MissEfish]

There aren't any visible sores and the barbels seem normal but he does seem a little bloated compared to the other three.

 

[WILDER]

I would feed them some peas.
Cook some frozen peas for a few minutes, let cool down, pop out of shell, mush between fingers, and add to the tank.
You might need to use anti internal bacteria med by interpet.
Taken from the above link.
http/www.aquariumconnection.com/saltsol/disease_desc.html
Bacterial Infection
Recognizing, diagnosing and treating bacterial infections is not an easy, straight forward task. Bacterial infections may affect internal organs, external organs or both and more than one pathogenic organism can cause similar symptoms. Bacterial infections can stem from many causes, even combinations of contributing causes, and result in potentially fatal diseases. Fortunately, most bacterial infections in saltwater fish are manageable if caught and treated early enough.
Symptoms:
Rapid breathing.
Reddened and frayed fins, or red streaks through the fins.
Disintegration of the fins (fin and tail rot).
Redness, streaks or blotches along the lateral line.
Open sores on the body and near the fins.
Bloody scales at the base of the fins.
A gray film over the eyes and/or body.
Loss of appetite.
Listlessness or lethargy.
Abdominal swelling or bloating - in saltwater fish frequently indicates bladder infection.

 

[MissEfish]

I tried the peas last night and everyone in the tank seemed to love them except the sick Cory. He actually ran away from the food. I tried again this morning. The Cory is now compleatly white and not eating anything.

 

[WILDER]

Has his breathing got harder.
I would issolate him and try a bacterial med.
Being listless and pale or darker in colour and not eating are signs of a bacterial infection.
http/www.petsforum.com/cis-fishnet/afm/G29060.htm
Taken from the above link.

The third type of infection produced by Aeromonas is by no means the least. This form is often the most virulent (potent) and can be rapidly fatal. This insidious form does not produce any noticeable external ulcers. The most notable feature is a behavioral change in which the infected fish generally become listless and lethargic. Some fish may lose color or appear darker. The fish do not feed, frequently seem off balance and may sink to the bottom laying on their sides. The course of the disease is rapid, and by the time the behavioral changes are noticed, the entire population of a tank may succumb, sometimes in a day or so. This is an internal infection, with the bacteria being found in the kidneys and blood of these fish. The bacteria produce potent toxins that account for the severity of the disease.

 

[MissEfish]

I have the sick Cory isolated and am treating with an anti-biotic. Now that he is on is own I can see a small red sore on his side. What about the other fish in the main tank? Do you think I should move the other Cory's and treat them all as a preemptive measure? Is there anything else I should do to prevent the other fish from getting sick?

 

[WILDER]

Just daily water changes usually on the main tank.
Its up to you if you want to treat the main tank as well.
Good luck.