They will uncurl almost immediately after they are born and will make their way to the surface, where their swim bladders are filled with air for the first time. The best time to net them is when they begin to near the surface. As soon after birth as possible, remove the female guppy to another aquarium by herself. While well-fed guppies do not usually feed on their own young, it is always best to play it safe. Observe the new fry for at least a week.
Fry food is available at pet stores.
It is powdery in nature, so avoid over-feeding as this has a tendency to clog the filter. If you observe any deformed guppies, remove them immediately. It is possible to begin determining the sexes and separating the fry after the initial week. Experts have a procedure for sexing the fry that is easily reproduced by a home enthusiast. First, you will need a two-gallon aquarium and a piece of black cardboard that can cover the back of the aquarium.