I started off feeding my Leaf feeder guppies. Concerned about transmitting diseases to my tank, however, I tried flash-boiling feeders to sterilize them. The Leaf eats the dead boiled guppies as readily as the live ones. I'm guessing it recognizes the shape or smell of the fish, rather than relying on a specific type of movement. I'm not sure if important nutrients are lost in the brief cooking of the fish, so I may supplement the diet with the occasional zebra danio or other small fish.
It definately only eats fish though. It initially seems interested in insects or worms, but loses interest once it figures out that it's just a bug.