Africans love frozen spirulina cubes. SA love frozen beef heart cubes. Just don't feed the Africans beef heart. They also both love brine shrimp, they go insane for it. As far as pellet food I wouldn't feed them anything but New Life Spectrum.
Also if you don't fertilize your lawn you could go out and pluck some earth worms out of the ground. My boys and I have done that and its pretty entertaining. Its like watching a game of capture the flag.