Try pellet....might just be what he's used to. Either way if he goes a good week w/out food it shouldn't kill him and he'll start eating flake or whatever. Tell him to have a nice warm glass of shut the he11 up and like it!!
i bought a FL last week and it started eating straight away. I've been feeding it Tetra Colorbits and Hikari Gold sinking pellets. Did you get it from a LFS? If so ask them what they have been feeding it.