I'll try some krill later.
He is a picky eater though. He's always refused to eat the food thats in the form of the "cube" or the "block" of food. I finally got him to eat the silversides when I got them in the individually frozen... units. I usually cut a silverside in half or third... depending on size, and then put it in front of him.
I also have krill, as that's what I feed the puffer, and he never seemed too interested. I'll try putting it infront of him (with a feeding stick, of course