Before purchasing moss, consider what animals will be living in the vivarium. Many animals, such as dart frogs, do not truly benefit from moss. Although it looks great, moss should not be the main ground cover in a vivarium. Most species of dart frogs kept in captivity appreciate a good layer of leaf litter and all the benefits it entails (hiding places, visual barriers, increased microfauna levels), and moss does nothing for them. Moss should be used as an accent – something that looks nice, but should not ‘take away’ from the needs of the frogs.
Remember, although moss looks great, it really does not benefit the frogs much. A good layer of leaf litter is far more practical.