as mentioned they are good at eating leftover food that they like, BUT once they are full they won't touch anything. they also won't eat scraps and pieces that are too small compared to their bite size. They can also be messy eaters. If you are looking for a fish that will eat ANY leftover and scraps and pieces, bichirs might not be the best choice. some bichir keepers actually get other fish to clean up after the bichirs.
also some bichirs will grab food from the surface, but most of them won't.