This is a creeping plant that grows on rocks, bogwood, etc. It thrives in dim light and likes warm temperatures. You should, however be careful when purchasing this plant. There are many mosses tagged as Java, but many of them are not meant to be grown underwater. A good dealer will know the difference. The genus name for Java moss is Vesicularia Dubyana. (Note: Many companies claim to have this in stock, only to give a substitution)
NOTE: This is "real" Java Moss (Vesicularia Dubyana), not "Willow moss" that most other companies try to substitute.