A rather out of condition male Carpintis... Has fin rot and hollow belly.
I don't see evidence of fin rot, it looks like a fish that has been beat up and harassed. Clean water, some kosher salt, and a good diet and he should bounce back in time. With fish in this condition I like to feed NLS Hex-Shield for a few days, just to clean them out. A follow up with PraziPro wouldn't be a bad idea either.
The edges of those fins are braking down so It is the early stages of fin rot... The fins haven't yet developed a secondary fungal infection but if left untreated it will.