- Small fish, such as anchovies, sardines, and silversides
- Crustaceans, such as shrimp, crabs, and krill
- Mollusks, such as clams, mussels, and squid
- Worms, such as polychaetes and lugworms
- Echinoderms, such as sea urchins and starfish
The specific diet of a flounder fish depends on the species, the size of the fish, and the availability of food in its environment.