Doesn't it depend on where you get water, and what fish and plants you keep? For example, I just started a planted tank, and I want to put tetras in there. It's a 50-gallon tank, and even if I house 50 tetras in it, I don't think their Co2 and waste will be enough for the plants to thrive. So...
I have some kuhli loaches. The rocks that form the caves at the bottom are glued together and they are resting on top of a thin layer of aquasoil. They can stand up on their own, even without the substrate/soil around them. The one on top of the hill has some volcanic rock underneath, too--it's...
Update! That comment from @Colin_T made me rethink my scape again. So here's version 3, with a little bit of water.
The plant stocking was disrupted by the missus, so the original plan is out the window. We went to 2 LFS and she got the plants she wanted: UG for carpet, a bunch of red plants...