Corydoras With White Slimed Thin Film And Red Belly

[Sparrowbell]

I have one corydoras has been covered with white thin films for weeks., some lesions. Then, red belly developed.
I have 55 gallon and other fish, some scaleless, who are/were till medications.

Despite all these skin lesion, the Cory appears to be active and have healthy appetite. I started with antibacterial treatment, Melafix. Though it looked better before got worse again. Switched to anti-fungal, didn't think it did much. Then, I finally moved on to anti-parasite medication, Paraguard. Didn't do the first week (killed my old pictus and knife fish in the process), but after stopping the medication and water changes, he seemed to have reduced white film but not getting any better. My iridescent shark also recovered from the over medication.

Out of all the corys, he is the only sick one, and out of the whole tank. Given he is in the tank all the time, I it is either fish are immune or not showing signs. Wonder if anybody thinks parasite is the culprit? I am thinking about moving him to a 1.2 gallon tank I just bought. What combination of treatment would u recommend? A bit hesitant as I worry I may kill him in hospital tank while he seems to be eating fine except for the skin lesions.

I have water balance issue prior to this and was resolved after I installed UV sterilized, probably help to prevent further outbreak.

Thanks,

 

[sonicboom81]

What are your ammonia, nitrite, nitrate and pH readings?
 
If you are setting up a hospital tank, it can be helpful to be able to put an established filter into it (as well as tank water). Air sponge filters are really good (and cheap) for this, and can be adapted to run on existing filter sponges. A cheap and bigger hospital tank could be a good sized plastic storage box. That's what my cory is in just now. About 3 gal+ box. Room for a heater. The extra water makes it easy to dose medications as well as maintain a more stable water quality.
 
I was told in a thread about my sick cory to make sure that there is substrate in the bottom of the hospital tank too.
 
I don't know what your cory has. What is the film like? To me it sounds like a bacterial infection, but I'm not as clued up on fish disease as most. Columnaris somewhat fits your description, but would kill fish quickly.
 
I made a silly mistake with treating my fish recently and medicated them with carbon in the tank, probably making the medication ineffective. So don't make that mistake If you could take a photo it could be helpful.