So far, I've been feeding infusoria (I'm not sure if my culture actually worked or not, but I still feed it just in case) and just a little First Bites. The fry are so small it's tough to imagine them getting any, but I'll just work on keeping the water clean. I also got the microworm culture in the mail, so I'll get that going as well.
The fry are definitely growing. I'll get some pictures this weekend, including mom and dad betta.