I would feed something like krill/shrimp/worms so if he has air bubbles that will clear them and if he keeps getting them because he is hungary they will stop. Something with bulk that will clear anything in it's stomach.
Sounds like it could be constipated. feeding him something with "bulk" could just bung it up even more.
It could just be serious gas.
Feeding pellets that have "gone off" can cause this.
The rotten pellets produce excess gas in the stomach.
You could try an epsom salt bath.
This will flush it's system.
I would feed something like krill/shrimp/worms so if he has air bubbles that will clear them and if he keeps getting them because he is hungary they will stop. Something with bulk that will clear anything in it's stomach.
Hopefully, no permanent damage was done. Polys are fairly tough.
I will do the epsom salt bath tomorrow. This is kind of a last result deal. I am worried that he is running out of time.