On a small scale the best bet is to strip the fry before they spit and rear them in a large aquarium to around 1"-2". Have separate tanks for each group of the same size up to about 4", then they can go into a community tank.

A fellow that gave me my basic tilapia training did it on a larger scale. He built a cage 3'X3'X6' out of PVC pipe and covered it with netting with 1" holes. He would put the cage in a small swimming pool and pill it with a breeding colony, a large clay pot for spawning, and some large PVC pipes for the females to hide in. Once he saw fry he would move the cage, fish and all to another pool. Be sure the cage has a closure at the top so the fish can't jump out.