Java moss is a slow grower, in my experience. How much light you have over the tank will greatly influence how fast it grows. In my 10g tank, there's about 2 wpg
(watts per gallon) above it, so it grows faster than in my 29g tank with 15 watts over it. If you want the moss to grow on something, you can do a few things:
1. wedge the moss between 2 ornaments, or an ornament and the wall, make sure it isn't getting pinched off, and just leave it.
2. If the water flow is favorable, position the moss so the water pushes the moss against the ornament
3. If all else fails, you can tie it with fishing line to the ornament, or rubber band it.
I just let my moss grow out, and it looks awesome! I need to get some pictures up, but I've got this big piece of "bowl" rock, and my java and christmas moss is all over it, growing into the rock, which looks really cool. I think it grows slowly onto things though, to ensure a proper grip.
I'm not sure what exactly your asking, but your moss will never grow on your heater. It needs a rough surface to grow into, and glass is far from rough