they eat live food that can fit in there mouth u can feed flake if they will accept but slim. i feed mine black worms and when he gets bigger im gonna feed some gost shrimp and krill. but i suggest black worms or blood worms u can also feed adult brine shrimp. but u can try anything u like.
Had a large one a long time ago (RIP). He stayed fat & healthy for years and I don't remember ever seeing him eat. He was such an elusive eater that I didn't think he was eating anything at all for a long time after a got him. I fed mostly frozen shrimp & blood worms alternated with tetramin flakes that I sunk into the water. I'm guessing he was happy to suck anything out of the gravel he could find while I was asleep.