there's probably no "best" food for dempseys or any other fish but in my experience, most cichlids prefer foods that sink, at least slowly. floating foods require that the fish leave the safety of the bottom and head for the top where insecurity results. i feed a great variety of food to all my cichlids .. among my top choices are Tetras Jumbo Min. if you squeeze it between thumb and forefinger before dropping it in the tank, it will sink slowly and break into smaller pieces as the fish attack it. i also use Tetra Krill, again crushed to facilitate smaller cichlids feed on it ... i've never seen a cichlid refuse either of these.