The first days
Many egg-layer fry live on their yolk sac for a day or two, then need food small enough for a mouth you can barely see: infusoria (single-celled life that grows in a jar of tank water with a little vegetable matter), green water, or liquid and powdered fry foods.
The next weeks
Once fry are visibly larger, add microworms and freshly hatched brine shrimp. Both are easy to culture at home: how to hatch brine shrimp. Crushed flakes and micro pellets follow as they grow.
Keep the water clean
Frequent small meals mean more waste in a small tank. Siphon leftovers daily and change a little water often; a sponge filter protects fry from the intake.