Use an air operated sponge filter in the fry tank.
If you have floating plants and no plants or rocks on the bottom of the tank, the babies will hide among the plants at the surface. Then you can gravel clean the substrate into a white bucket and let it settle for a few minutes before looking for babies that might have been sucked up.
If you have floating plants and no plants or rocks on the bottom of the tank, the babies will hide among the plants at the surface. Then you can gravel clean the substrate into a white bucket and let it settle for a few minutes before looking for babies that might have been sucked up.