Originally Posted by callistra
Great ideas. I thought about obsidian but afraid 10-15lbs of it would be an arm and a leg.
The pool stuff is cool because it's sparkly.
I think my favorite are the natural black beach pebbles.. if I can find them. I'm in the US.
obsidian's not actually that expensive, unless you're looking for large (bigger than a quarter) sized pieces or shaped pieces. i've seen bags of tumbled obsidian in mineral shops for $15-20 that would be just wonderful as a base for a black rock tank, and pebble/bead obsidian in craft stores that's even cheaper. mix those assorted pieces with a bag of black gravel and you've got a nice, upscale, variegated black substrate for a lot less than you'd think.