Do I still need to feed the guppy fry?

Mine survived in the tank with the parents and without live plants just by scavenging the flakes that I fed to the adults. I wasn't really going for maximum survival though. What I did allowed like 3 to 6 babies to live. It was nice because it would be fresh new fish but not overpopulation. If you want more than this, try brine shrimp and fish flakes crumbled up real well and a lot of hiding places. Egg will will work too but I expect the brine shrimp will be hardest for the parents to eat all of.