I assume in a fish tank? go to the pet store and buy a pack of frozen bloodworms. Feed them those until they are big enough for spikes (maggots), then move to waxworms/earthworms, then to small minnows and worms mixed.
To feed the frozen bloodworms, thaw in a small cup of water then use a toothpick or tweezers to place them in the water. once they realize its food you can just toss a block in the water and they will eat them as they melt.