Give him a little while. Try starving him for a couple days then try some prepared foods. You can try krill, prawns, sticks, etc. If he won't take those right away you could try some gut loaded crickets. These will float at the top of the tank and get him used to taking food off the surface. Get him on those, then alternate dropping crickets in with some other prepared food. Keep adjusting the ratio so that he is eating more prepared food and eventually he will eat that right off the bat.
Definately get him off the goldfish though. They guy at the petstore was right; they're no good at all.
Definately get him off the goldfish though. They guy at the petstore was right; they're no good at all.