What Is This?

[Michelleuk]

I am posting on behalf of my uncle so dont have all the details.
 
what could this big bubble thing be on the fishes vent.

 

[bluesword23516]

I have never had angle fish but maybe if it is female it could have a prolasped uterus. 

 

[Michelleuk]

any one got any ideas how to treat this?
 
thanks

 

[fluttermoth]

It does indeed look like some sort of prolapse or hernia.
 
I'm afraid there isn't anything you can do, apart from keep the water in tip top condition (so, plenty of extra water changes) and keep your fingers crossed. Fish are remarkably resilient and it may be able to pull through.

 

[star4]

Ditto FM clean water is the best option. This can happen with fish "practice spawning" I have an elderly flier cichlid that fertilizes wood, rock etc and ends up with damage to his bits, but it usually does down after a few days.