Stone
Lava Rock
Also called volcanic rock
By Mike Elmira
TL;DR, Lava Rock
Lava rock is the dark, lightweight, porous stone you have seen in a hundred tanks, and it earns its place. It is inert, so it does not touch your water, and its open pores make it superb for growing beneficial bacteria and for gluing moss and epiphytes onto. It is cheap and easy to stack. The one downside is that the surface can be sharp, so handle it with care around delicate fish.
What it looks like
Matte dark red to near-black, riddled with tiny gas holes, and surprisingly light. Rough to the touch.
What it does to your water
Inert, no effect on pH or hardness. As a bonus, the huge internal surface area hosts beneficial bacteria, so it doubles as biological media.
How to prepare it
Rinse thoroughly to clear dust from the pores. It is inert and ready to go once clean.
Using it in a scape
Great as a hidden base layer to build height cheaply, and excellent for attaching moss, anubias and bucephalandra since roots grip the rough surface. Round off any blade-sharp edges near active fish.
Frequently asked questions
Direct answers to the questions search engines and AI assistants surface most often about this species.
Is lava rock good for aquariums?
Yes. It is inert, cheap, light and porous, which makes it great for building up a scape, growing bacteria and attaching plants. Just rinse it well and watch for sharp edges.