Corys Are On The Lay

You have a few days to start a brine shrimp hatchery, tiny fry can usually manage newly hatched brine shrimp or you might be able to find a shop that stocks frozen baby brine shrimp (BBS).
As they grow, things like microworms are easy to culture. I've used that in the past, I just buy a starter culture from Ebay. All you need for those are a couple of tubs and cheap instant porridge. It does take a few days to get it going, then it is self sustaining, starting a new culture before the old one goes off. There are other kinds of tiny worm cultures, some are too big for newly hatched fry so do a bit of research before buying.
The fry might possibly be OK with decapsulated brine shrimp eggs.

When they get bigger, try cyclops (frozen from the LFS)

My cherry barbs have had kids and I didn't realise it for ages. They seemed to be quite happy munching on the algae and stuff that grows naturally. I've got one stuck in the refugium filter at the moment. He or she is quite happy living in there and when it gets big enough, I'll syphon it into a bucket and put it in the main section of the tank. I've not fed them anything other than the normal crushed up flake food and frozen food.