Depends how big his mouth is as to whether he can accept pellets, all mine have done from Bettaman even the tiniest plakat but if not you can just crack them between two spoons and it makes it easier for them. The usual foods yes, bloodworms, daphnia, artemia etc.
I've got one of his brothers and he has eaten blood worms and tetramin betta flake. He and his 3 foster sisters are all eating well I might add since they only arrived yesterday.
I had a betta get a pellet stuck in his mouth once. Not a fun thing. Since that day he hasn't tried another pellet. I tried enticing him, but no go. He gets bloodworms and peas instead. He's spoiled
My bunch is just starting their 9th week. In the morning they get betta bites - including the runts. At night the runts get chopped up enchanced brine shrimp and daphnia plus a few left over chopped up blood worms. The larger fry get chopped up blood worms and chopped up brine shrimp. I am beginning to notice that they really don't need them chopped up anymore.