1, fed too much.
2. The mother fish is pregnant with a small fish.
3, it is ascites.
Look at the state of the fish first, is it lively ~
Observe the feces of small fish. It doesn't matter if the normal black stool is thick.
If it is white feces, it is slender or filamentous. That is enteritis or ascites ~ ~
Need medication, very troublesome ~ ~
And there are many reasons for ascites, such as parasites, or food problems, many ~ ~
You should think more about what happened before. The right medicine ~ ~