Catfish and labyrinth fry especially will gulp air. If they are in 75 degree F water and gulp 65 degree F air, they could die. Most other fish can have up to a foot or more in depth and survive. Most egg-laid fry swim at the surface anyway. Lighting and cleaning It is also a good idea to add lighting above the tank for a few hours after you add food.
Newborn fry are tough.
Besides the filter and heater, the tank should be empty. This is so that once you start feeding, you can clean the tank. Use a piece of air line tubing or vacuum tubing to vacuum debris off of the bottom every day or two. Any fry accidentally sucked up can be pipetted or sucked back into the tank. Feeding One fry food is infusuria bought through the mail, cultured from ponds, or made at home with dry formulas you can buy.