Question about feeding betta fry brine shrimp.?

Ok i youtubed how to raise brine shrimp and i think im ready to breed bettas and raise the fry. But my question is, is it really safe to feed the betta fry salty brine shrimp? Are brine shrimp even freshwater or saltwater? What other foods do betta fry eat besides salty brine shrimp? Can they survive on just algae? Sorry for all the questions i just have a pion for these guys and it would be cool to breed them and raise them.