I was going to get a marimo moss ball, but when I got to the LFS all they had was an extra large ball, when I was looking for a medium ball. So I got a java moss ball. I brought it home and put it in a bowl with some tap water to kill any snails. Now I have questions on if the caring for it is any different from the marimo? Any other info is welcome.
Java ferns are extremely hardy. No or low light is fine for them. The only thing you need to do is make sure that you don't bury the rhizome. It can be left floating or tied to something else like wood or rock. :)
Quarantine it before adding it to your tank. Snails can survive a lot, and you don't want it to carry diseases.