First, if you raise the temp to about 80f and keep the lights on 24/7 it will speed up the gustation process. I don't recommend leaving the lights on like that for more than a few weeks.
Secondly, yes a growout tank is necessary. If you want to save fry and have a place for them to growout for a few weeks use a 10gal stuffed full of java moss. Either net fry when noticed or put females that are ready to birth in the growout tank. Give her a few hours after you notice fry and put her back in the main tank. You can get the java moss many places, the fastest is Aquabid.
Third, what do you have to feed these fry? Microworks, baby brine shrimp or the easiest Golden Pearls 200-300 microns works well. You can get the worms from Aquabid and I'd get the Golden Pearls from Ken's Fish. Any other questions just P.M. me.