I havent seen much on that knife. Likely breeding will be difficult.
Definately a nocturnal predator, depending on the size of the knife you can try feeding some guppy feeders or small godfish feeders. Its likely he wont show much action during the day. Knife fish are generaly very energy efficient. They rest well during the day and feed at night. So put the feeders in as you cut the lights out.
Its also possible that he may have a hard time getting food if you have other faster predators in the tank.