Springtails are tiny arthropods that live your terrarium as a clean up crew. They are perfect feeders for small species and also can be a great treat for larger species.
Purchase info: 
Springtails come in a deli like container. When you recieve your springtails please keep the container open a little to allow air to circulate for an hour. This way waking the alive springtails from a coma like state. Many will succomb to death but they replenish and bread quickly after feeding and proper care.