You have two possibilities.
one is catching the fry after release. After hatching the fry will swim to the water surface. If you have some plants floating on the surface its no normaly no problem for them to hide.
Btw i never had any problems with my calvus eating any fry. But i know that it can happen.
Or you can separate the females a few days before release. They carry their young for 18-21 days. But be carefull sometimes they spit their eggs or fry into the net while catching them. So the fry better be old enough.