This is mainly caused by bacterial and fungal infections.  The fins will look like torn and fragmented.  vigorous fighting of big and small fish may also result in condition that

In this disease, red colored part will be hanging out from the anal region.  In the initial stages of this disease,  red coloured hanging part will be taken back inside

This disease occurs due to more accumulation of fluids in the abdominal cavity.  Fish abdomen will look bulged and sometimes even eyes are also seen enlarged.  Concurrent failure of liver