White patch on Corydoras back - illness or damage?

[megwattscreative]

Hi all, hope you're well. Following my trials and tribulations with bacterial illness effecting my corydoras, I'd like to get a second opinion on whether this looks to be damage or a bacterial issue. This pygmy corydoras arrived from the shop with a white patch near to her dorsal fin, and i can't work out if it's damage sustained in the shop / before, or if it's a bacterial issue. I'm debating whether to dose with Esha 2000 again. Here is "ms patch":




I've edited the first photo to reduce blur but you can see it unedited further down. It looks as though the patch is almost diamond shaped when viewed from the front (can't get a decent picture), along the lines of figure B in this image:
however, it doesn't extend all the way down to the head.
Here's a pic of my other corys for comparisons sake:

The little one in the bottom is "finless" - he lost his dorsal either due to fin rot or nipping some months ago, and it's never grown back. However, he seems pretty chipper and confident in the tank - I often see him running off the tetras and shoaling with the other Corys. Any advice appreciated 🙂

 

[Bradders]

Hi Meg, are these new additions? And when you say arrived from the shop, were they delivered or you picked them up?

 

[megwattscreative]

These are the same additions from the journal, i haven't added any more fish since getting them a while ago. I picked them up 🙂

 

[dw1305]

Hi all,

I'd like to get a second opinion on whether this looks to be damage or a bacterial issue. This pygmy corydoras arrived from the shop with a white patch near to her dorsal fin, and i can't work out if it's damage sustained in the shop / before, or if it's a bacterial issue.

It looks in generally good condition, so I'm going to say it probably isn't bacterial.

Even though I have Corydoras pygmaeus I see them very infrequently and never know how many I have (but at least 10 at the moment, some I bought and some bred in the tank). This means some must have died (or I have more than 10), but I've never noticed a sick or dead one, so I can't really add anything useful.

The little one in the bottom is "finless" - he lost his dorsal either due to fin rot or nipping some months ago, and it's never grown back.

It won't grow back now, once the fin rays are damaged to the base they don't grow back, but it doesn't matter to the fish and it looks fine.

cheers Darrel