Advice please on goldfish with a swelling on its side.

[wardpf56]

We have today rescued some fish from a person wanting to get rid of their pond.

Two of the fish appear to have a swelling towards the rear of their bodies. Can anyone advise what might be the problem, please?

We have isolated all the rescued fish before letting them join our existing stock in the pond.

The attached photo, hopefully, shows the two fish raising my concern.

Thank you in advance.

 

[j.w]

@wardpf56
Not sure but could be egg bound, dropsy or swim bladder. I have had fish like these and I did not know what to do so I just left them be in my pond. They lived a long time (years) like that but finally died.