Fry are always nervous of becoming a meal for larger fish, ...even their own kind. Provide them with some surface vegetation to provide them some sense of security. Then, offer live fish as food. Once they're feeding you can wean them onto floating pellets/sticks/FD foods. All of my new gars were quick to get on sticks when I placed them in with fish that already feed on floating prepared foods. They pick it up more quickly when they learn by example.
In single-specimen tanks, I got my trops onto prepared foods by feeding them live feeder minnows, one at a time and always at the same spot, before starting to introduce sticks. Then, I'd drop a minnow followed by a stick. Once they start snapping at the sticks it's a simple matter to increase the ratio of sticks versus minnows until they're completely on sticks.