Pictures of the fish?
What does the fish's poop look like?
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so, what is it?
Intestinal worms, internal bacterial infection, she didn't drop all the fry and still has some in her.
If the fish is eating well and doesn't have scales sticking out around the belly, it is either worms or unborn babies.
If the fish is no longer eating then it is probably an internal bacterial infection.
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To stop them eating their young, feed the adults 3-5 times a day with a variety of food so they are full. Fish that are full will be less inclined to eating their young.
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You shouldn't move female fish that are pregnant/ gravid or that have given birth in the last week because you can injure them internally. If you have to move them during this time, catch them in a net, then put a small plastic container under the net and lift the fish and net up in the container of water.