Davallia parvula

This miniature fern only grows to about 1.5 inches tall, forming dense mats in the terrarium given time.  It prefers to be mounted to something, rather than growing on the foreground.  Treefern poles work wonderfully, as do cork and tree-fern flats, and likely most other wood surfaces.  This species enjoys high humidity, with some opportunity for the leaves to dry out between waterings.  It is found in Borneo.