cut up pieces of earthworms, eventually he will grow to take the entire worm in one bite. My clown knife has grown to 18" and still growing. I also feed him raw shrimp
He likes to stay at the bottom. I tried the foods that where sugested but he just wouldent eat. The only thing he did eat where some very small feeder fish.
you got him hooked on feeder fish, this is the reason why I never fed my clown knife feeders also due to the fact that some feeders may not be very healthy and thus may harm the fish