Java Moss can be grown as a tight "lawn" covering a coconut shell. Prepare the coconut shell by covering it with boiling water and steeping it overnight to leach out some of the tannins. Now get a large enough glass bowl, under which the coconut shell can stand without touching the sides, and a glass plate for it to stand on. With a scissors, snip half-inch snippets of Java Moss and let them fall all over the coconut shell. A light spritz from a mister will settle the sprigs flat against the coconut fibers. Pour half an inch of water into the bottom of the plate and cover it with the glass bowl. Then set this mini-terrarium that you've created into a brightly lit north window, where it doesn't get direct sun. In the bright humid atmosphere, the moss will revert to its denser, ground-hugging terrestrial style. If the moss gets to looking dry, I spritz it. In a very few weeks, when light green growing points show all over the moss, you'll know the moss has taken hold of the coconut fibers. Give it a gentle rinse to dislodge any snippets that didn't take, and put the greened-up coconut shell into your aquarium. You can pull it out again once every six weeks or so, to clip the "lawn" very close with the flat of the scissor blades.
