What wrong with my phantom tetra??

[Kate14]

my black phantom has this white sac that looks like its coming out. Still active and feeding. Tried to do the best photo, but shy fishes!! Any advice?? Tia

 

[MattW]

I wonder if it is a rectal issue? @Colin_T will have a much better idea than me

 

[GaryE]

It looks like a prolapse. The abdominal wall is weak, and the intestine is protruding. If you stop feeding him, there is a slight chance it will go back up. But even if it does, the hernia is still there, and it will return to eventually kill the unlucky fish. Sorry. It's one of those things we can do nothing to cure.

 

[Kate14]

Thank you both for your help. Still with me this morning, but will keep an eye and see how he gets on