Sad Cory

[RovingGinger]

Yesterday I noticed one of my smallest julii corydoras sitting on some java moss not as active as the others. Today I observed the same thing - not really romping around, just sitting still - and the bottom part of his back fin looks chewed. I don't see redness, etc, or other damage to him. The tank is a 40 breeder with 7 other julii corys and a bunch of mutt guppies/endlers of all ages. Is he simply getting picked on for being kinda small or should I be looking for something else? I have him in a separate tank right now and will try to add a photo.

Edited August 11, 2020 by RovingGinger
Added sad cory tail photo

[Daniel]

How is sad cory doing now?

[RovingGinger]

He's hanging out in a small tank with a couple of bent guppy fry, can't really see anything behaviorally off. He seemed a little skinny comparatively so I'm thinking maybe he's just struggling to compete with the big guys a little and maybe underwent some tail nibbles, but I'm not seeing signs of anything more. 

[Mark Mason]

I had one of my J Cory's hit the top lid hard and he was down for a week but he recovered hope the same for you

   

[Brandy]

If he's small and lethargic, would internal parasites be a possibility? I don't know anything about how prevalent they would be in corys?

[RovingGinger]

Community ecology of parasites in four species of Corydoras (Callichthyidae), ornamental fish endemic to the eastern Amazon (Brazil)

WWW.SCIELO.BR

 I didn't read the whole thing but it would appear yes, at least in general in wild caught they would be. He was a petco boy so that might be a possibility.

The fin doesn't seem to be getting worse and he was eating yesterday, so I'll see if he continues to be skinny on his own? I don't expect him to be terribly active without his friends.

[MR aquarium]

if he is a very young/small cory then it could be possible that he got his fin lodged in the filter and it may have ripped of that is the only thing that i can think of for the cory getting stuck somewhere. as for being inactive i would say it is normol for a injured fish to be laid back and not move much i have had corys in all my tanks and that is the most likely things that i can think of. he should heal up real well if you keep water conditions good.