Gatekeepers of Nalanda

Source: Ancient Indian Riddles http://bronze.uco.edu/

This riddle was used by the gate keepers of the Nalanda university as the
entrance test question(Nalanda was the first completely residential university
of the world to have entrance examinations, and the gate keepers used to be
most sound brains of the campus who tabbed the entrance of the candidates)

Problem:

A spirited jig it dances bright,
Banishing all but darkest night.
Give it food and it will live;
Give it water and it will die.