Very cool knife.. if they 'lay' around don't panic.. this is there normal behavior..
They love frozen foods, any type of worms.. crazy for blackworms, but will sniff out bloodworms/mysis shrimp, etc.. mysis shrimp is way better than any other frozen food like brine shrimp, more protein, less water content..
careful of competition for food.. I took one home and put it in a very packed community tank, and it was very reluctant to come out and compete for food with all the loaches and tetras, remember they are electrical, so they sense the over activity of other fish like that.. Had the same issue with the glass knives.. eventually they start to waste away from lack of food - especially since they want to feed at night.. they are always 'tails up/heads down' at night cruising around, but if you have corys or loaches they won't find nothin..
good luck!