shrimp, floating pellets, fresh fish fillet, insects....the list could go on. for some reason mine tend to favor freeze dried krill, hikari cichlid gold floating pellets, and raw shrimp the most. they show less interest in raw fish... although they will readily eat it.
i got a needlefish a few weeks ago and he would not eat anything but live the first week........ than i just tries frozen market shrimp and krill and now he eats it like crazy. you might have to starve him for a while though.
i almost got mine on pellets they will eat cichlid food sticks but only when there wet and are soft i'll try to post pics of mine gulping down something but i think any true gar would out grow a needlenose gar and would eat it spotted gars get around 3'-4'