I have had my african knifefish in my tank for 5 months and it does come out what is the problem. Is it possible that he is scared of my 8.5" Tiger Oscar or is it just their nature.
The African knife like many knife fish are nocturnal. Have yo tried turning the aquarium lights off and leaving a lamp on in the room. Your knife may be more active than you think. Also they make a type of moon light lighting. I have heard that knife fish like this type of light as well.
I feed my peacock eel bloodworms and earthworms don't know if at 2" it would be able to eat bloodworms thought. You might want to try and get one around 5" or so I got mine at 6". Good Luck