I say use sand. It makes a good natural filter. All the organism that live in the sand are good for the tanks environment. But what ever u do don't use sugar grain sand. It's to easy to have sand storms with sugar grain.
I miss the natural sand look, but you can't beat how easy it is to clean a bare bottom tank. Detritus collects usually in one spot and it takes seconds to clean. If I only had one tank I might do sand again.
You can do a mix of different grains that looks kinda cool where all the smaller sugar grains will settle on the bottom with larger grains on top, kind of a layered effect
