Java Moss its quite an easy plant to keep. They prefer cold water and less light, but their growth is very slow. I went to collect some in the wild where it was growing in its emersive form. This moss was located just behind my house in a palm oil plantation. To find this moss, they only grow under the shade of trees and in very wet conditions. This plant can be tied to driftwood or rocks, or can be laid on the substrate like carpet; but it can sometimes get messy.
More infos about Java moss, you can go to: aqua moss
Enjoy the pics!
You can see the pics of this type of moss growing submerged/underwater after a month in my tank here : Submerged form of Vesicularia dubayana