You can take them out as soon as they're free swimming. You can siphon them out with a turkey baster or any hose for small enough fry an air hose works. You'll want to siphon them into a small tank, like a 5 gallon, with a sponge filter so the density of food remains higher and easier for the fry to find. Do something like two water changes a week or more, siphon uneaten food with a air hose and watch them wrigglers grow. You just have to stay on top of water quality with a small tank like this and the multiple feeding to keep the fry nourished.
The only problem is you'll need food thats small enough for them to eat. I've had success with Hikari first bites. You only need very tiny amounts (1/4 pea size pile) multiple times a day. This has worked with convict, danio, and guppy fry. I've also used freshly hatched brine shrimp but its more labor intensive. Some people like to use cooked and mashed chicken egg yolk. Naturally you progress through the sizes of food as the fry grow something like daphnia or NLS grow pellets would be a next step up, then tubifex worms, then bloodworms and so on.
I raised the fry as feeders for stubborn fish like odoes or as treats for my other fish. Your breeding pair should spawn soon after removing the fry. Multiple chamber tanks work great cause you can have multiple sized spawns growing out like a little fry factory.
