Most common use: New hatched fry

Egg yolk is a good food for new hatched killies, especially for species that takes food from the surface e.g. like the Epiplatys. In old days the brine shrimp eggs were very hard to find and extremely expensive. One of the foods used instead was as simple as egg yolk.

Simply boil an egg in 15-20 minutes so it is well boiled. Pick out the yolk and save it cold. When feeding take a small cup of water and pick a small bit of the egg yolk between your fingers and sprinkle it in the cup. Eventually stir the water a bit and pour it in the fry tank.
The egg yolk itself is a good food but also the infusoria that quickly will develop around the yolk powder is essential and good fry food.

Be careful to very use small quantities as this food can easily foul a fry tank. Also remember very frequent water changes.