Betta keeping have always been in my blood and I first started breeding Bettas more than 15 years ago.
I used to feed the fries Liquifry but nowadays I do not do that anymore as I feed the fries live Daphnia. It does wonders for the fries and the fries grow up fast.
If you have fries to rear and grow, do feed them as much live food as they can eat. The fries will always be hungry and they will be looking for food as they swim around the tank. Hence it is always good to prepare some live food such as brine shrimps if you intend to keep the fries growing as much as possible.