Can't decide between rock and wood? Why not have both. Petrified wood has wood characteristics embodied in a stone-liked structure. A popular design recently made popular by Japanese Aquascapers, it is a fun piece of hardscape to work with. Glue in and make mountain valleys or create a simple iwagumi style scape, everything is a possibility. Plus, it is inert, no worries about getting your water hardness up.
