Yolk Sacs
Tadpoles don't eat when they first hatch. Instead, they consume their egg-sac as a food source. This will take several hours up to several days. When they begin to actively swim around the tank, they'll start eating their first real meal.
Wild Tadpoles
Tadpoles eat rotting and dead plant material, but they don't get much nutrition from the dead plants themselves. Their nutrition comes from decomposing organisms that are in the material they eat.
Pet Tadpoles
Feed tadpoles green leafy vegetables like lettuce or frozen endive. Freezing the endive lets the tadpoles get more nutrients out of it since freezing breaks up the cells. Tadpoles eat their own feces, so you shouldn't keep their tanks too clean. When changing the water, let the feces on the bottom of the tank remain as a food source.