UG can root onto other objects besides lava rock. A guy on a carnivorous plant forum I'm on, has experimented with it and this is what he had to say:I had no idea that UG could root on volcanic rock, that's friggin awesome!
I have grown this stuff in everything from rockwool, mud, gravel, clay pellets, moist driftwood, ADA aquasoil, sphagnum moss, other mosses, rocks, on top of other plants, on plastic (99% humidity tank, its growing on some worm feeders), on top of airline tubes, glass (its growing on the side of the glass in a 99% humidity tank, on the side nothing holding it there) and probably a few more things I've forgotten about. It has grown in every medium just fine under alot of different lighting levels. I have some growing under a single 14W compact flourscent, all the way up to some growing under 4 T5HO bulbs and lots of levels between.
I have my UG growing on an Exo-Terra Waterfall, some of it is completely under water, some of it is in the waterfall's current.