Cory with tail fin issue

[meadeam]

One of my cories I have just noticed is missing part of his tail fin.  I am fairly certain he hasn't been nipped, and none of the other cories have a problem.  Since I noticed is fin I've been looking for nipping behavior and haven't seen any.  The particular cory may have got the short end of the stick genetically.  The poor guy doesn't appear to have eyes.  It has never kept him from finding food, and he has done well up to now.  He can still swim, just looks rough.

I hate to treat the tank for one fish.   I'll stay really on top of the water parameters and keep an eye on him.  I suppose it is possible I let the nitrates get too high in the past.  They were 20-40ppm today and I did a 50% change this morning.  Any suggestions are welcome.

 

edit: to be clear, he has eyes, but they are tiny specs and I am pretty sure he is blind.  He's been that way since bringing him home, long before the tail fin issue.  I know missing eyes could be a sign of attack, but want to be clear that he has never been picked on.

Edited September 19, 2022 by meadeam
add'l info

[Guppysnail]

I’m sorry your little one is struggling. Photos of the fish in question will help folks help you. Very hard to say anything without seeing it. 

[meadeam]

On 9/19/2022 at 2:17 PM, Guppysnail said:

I’m sorry your little one is struggling. Photos of the fish in question will help folks help you. Very hard to say anything without seeing it. 

yeah, I'm trying.   He was out front this morning and I should have grabbed a pic, but now he has retreated into the plants.  I generally see him several time per day though.

[meadeam]

Here is a shot of the one in question, and three others.  Man he looks rough.  Still no sign of him being picked on though.  Now that I am scrutinizing them  I feel like they should all be fatter.  I feed heavily enough that food makes it to the bottom, and I drop pellets and wafers down to them.  I actually feel like I feed pretty heavily as I often see the other fish stop eating when there is still food in the water.  

Edited September 19, 2022 by meadeam

[Nina]

Hmm, maybe fin rot? I have a very similar issue in one of my albino Cory's -- three are perfectly healthy, but one has almost no top in and is missing part of his back fin.  It' been that way for months, so I don't think it's anything aggressive, but I'm thinking about putting him a hospital tank. He seems so happy with his buddies that I hate to, but I'm also worried he could spread it. I may use API fin and body cure. Not sure yet. 

[meadeam]

It's a tough decision.   I think for now the plan is to maintain the tank as dutifully as possible and see how it goes.  

What other parameters can I test for that might uncover a problem?  Phosphates?  Copper?

Edited September 19, 2022 by meadeam
Weird double post on mobile

[meadeam]

So I have a different sort of theory now after thinking about it for awhile.  I think this Cory is probably immuno compromised and is expressing an illness that is present in the tank, but the rest of the fish have been able to fight off with their healthy immune systems.  I'm leaning toward treating the tank for finrot for fear of more fish getting sick later.

Thanks in advance for your thoughts, opinions and advice.