ok thanks for the reply.....been about a week and a half so far......its great being able to watch them grow alittle every day!!! will keep em in for a good fews weeks yet.Welcome to the forum Fab71.
A lot depends on the size of the other fish in your main tank area. If you have only platies, the fry may be big enough to do well in about 6 weeks of growing. If you have other fish in the tank, you need to guess how big a fry those other fish can swallow. That would be the minimum size for the fry to be safe in the main tank.