Affected fish show abdominal distention (fish look like they are ready to spawn), caused by a sac-like formation with watery or mush-like content.
It develops chronically and therefore is often revealed too late when milt or eggs have already undergone changes. Disease is caused by separating males and females for too long and feeding them too much unvaried dry food. In advanced stages, fish cannot spawn and, as a rule, die.
How to cure:
Disease can be cured only if caught in the early stages. Put the fish on wet cotton wool and squeeze out the content of the cyst though the anus by carefully stroking the fish from the pectoral fin to the subcaudal fin.
To prevent the disease, provide your fish with a varied diet of live food and pair fish timely.