When the gills turn out to be inflamed and swollen, it is a sign that the fish is suffering from branchiitis. This disorder might be accompanied with white patches on the body along with a general listlessness.
The trigger is lack of accessible oxygen in the water, which is, in reality, asphyxiating the fish, this causes the gills to turn out to be inflamed because of being overworked.
The fish should be transferred to the hospital tank, in which the water level has been reduced to about 6 inch. The water should be aerated, and also the fish fed with little quantities of live food. The condition should clear up within 10 days.