I have java fern out the ears, almost literally. I am seriously pondering trying it out as a salad vegetable. Or you know.. giving a ton of it away.
Mine grows like mad, sprouts babies all over and stays very green aside from spore-spots and the odd elderly leaf.
The secrets of rampant java fern growth:
-- Absolute neglect. No ferts, no nothing. Tether it (or not) then leave it the heck alone. Well, that's what I do, anyway.
-- Low lighting. It actually does way better in the darkest bits of my tanks, and under weak LEDs that ought to be replaced. That's where it's growing like a weed. Oh, and in a heated bucket in my laundry with hardly any light at all.
- Soft water/acidic water. It doesn't like alkaline conditions, probably as it evolved in high tannin blackwater under some serious forest canopy (hence it likes low light).
-- NEVER put it in the substrate. It likes being tethered to driftwood. Though I have clumps growing loose and some tied to rocks too, and they're all doing about the same.