They were probably done for before they ever made it to your tank. Why not buy some form MiniFishRoom next time around? If his really eat flake i would jump all over that!
If you do end up with wilder ones in the future though, microworms are a good one. Daphnia would help as well. I believe they will take frozen brine, but i would NOT feed anabantoids, or most any fish, bloodworms. Way more trouble than they are worth.
The ones i had some years back took decapsulated brine shrimp eggs, they may have taken golden pearls but i fed them at the same time and it was hard to tell the difference. They also ate pond snails I crushed on the glass. I kept CPD's in the same tank and they spawned every morning, i imagine they got a good supply of fish eggs this way. Lots of plants and mosses help to grow copepods for them to graze on as well.