Fish often stop eating when introduced into new surroundings. It's worrisome because it might indicate a more serious problem. JDs are quite carnivorous, so the way to get them to start eating might not be with staple food, but with something more enticing. Tiny shreds of fish, ham or chicken might work. If the fish is very small, bloodworms might be the right size. Hot dogs and chopped earthworms later on (not too much as this is quite fatty). When feeding shredded fish, use saltwater fishes. There is a lower chance of spreading pathogens from saltwater fishes to freshwater fishes. Of course, there's even less pathogen vectors feeding shreds of ham ; )
NetMax