[andrewg]

Lava rock is probably one of the best rocks to grow moss on, and I have heard some people use very small, crushed pieces in their substrate to increase surface area for beneficial bacteria to live. And, lava rock can certainly accentuate an aquascape if used correctly. (not saying there is any correct way of course)

 

[andrewg]

You say lava flow, do you have any pictures of this behemoth. Lava rock is the porous, red/orange, very light weight rock. I think we might be talking about something different.