Corydoras on its side on the substrate

[RadT]

Later today I looked in my tank and I noticed that one of my Corydoras catfish is unwell. He's on his side but breathing, and he is paler than his other tankmates. I have 3 others in the 20-gallon tank, along with 3 Australian Rainbowfish. The other 3 corydoras and rainbowfish are perfectly fine. On top of this, I did a ~20% water change.
Unfortunately, I don't have any test strips with me and I will have to get a water test tomorrow. I don't believe it would be nitrates/nitrites, as it would affect other fish in the tank. Thanks for your time, I am very concerned about him.

 

[HoldenOn]

Parasite probably. Got pictures?
General Cure will fix it, if it is a parasite.

 

[RadT]

Parasite probably. Got pictures?
General Cure will fix it, if it is a parasite.

Thanks for replying! Here is a picture:

For comparison, here is one of his tankmates, the same species:
I'll look into General Cure. should I isolate him and apply it or should I apply it with him in the community tank?

 

[HoldenOn]

Thanks for replying! Here is a picture:View attachment 128419

For comparison, here is one of his tankmates, the same species:View attachment 128420
I'll look into General Cure. should I isolate him and apply it or should I apply it with him in the community tank?

Hm, the clamped fins aren't a good sign either. I'd love a picture of him on his side, but in all honesty I'd just go ahead and treat the whole tank with General Cure.

 

[mark4785]

The eye of the sick fish seems to be protuding slightly. I would guess that it has consumed something rotten from the substrate and developed a bit of a bacterial infection.

If I were you I would take it out the aquarium and put it into a separate new tank with no substrate for 24 hours so it is a relatively cleaner environment for it. Offer it some blood worms to help it recover.

In your main tank I would do a large water change and try to remove any rotten food that maybe in the substrate or accumulating in a dead zone.

 

[RadT]

The eye of the sick fish seems to be protuding slightly. I would guess that it has consumed something rotten from the substrate and developed a bit of a bacterial infection.

If I were you I would take it out the aquarium and put it into a separate new tank with no substrate for 24 hours so it is a relatively cleaner environment for it. Offer it some blood worms to help it recover.

In your main tank I would do a large water change and try to remove any rotten food that maybe in the substrate or accumulating in a dead zone.

I was thinking this is the reason too. While I haven't seperated it from the others, I have been putting in a bacterial treatment in the tank, so hopefully he can recover.