1. 5-8cm natural black lava rocks, with drilled holes / without holes.
Lava rockes is a popular functional and decorating rockes in bonsai, aquariums. They are natural filters.
They are porous to let water go thru.

2. I attached some photos of terrarium made of black lava rockes. In the Buddha moss wall terrariums. The saxifrage are planted in the drilled lava rockes.

3. In my terrarium projects, I plant small plants like fittonia, and small ferns in the drilled lava. I do that to restrict the roots so they won't destroy the live moss wall.
There are many other ways to use lava rockes for bonsai, moss and microlandscaping, like the one in the main photo. I glued lava rockes together and use red clay to stick the moss on them. The other moss project in the blue framed fish tank is made in the same way for one of my local buyers. It is glued lava rockes behind the moss.

4. If you do not want polystyrene to build landscape in your terrarium. Those rockes are best alternatives.

5. It is ideal to grow moss. Those with holes is made for planting small terrariums plants and will help you create a vertical landscape.

6. Ideal for container garden, jar, terrariums, aquarium, paludarium, vivarium.

7. It goes well with plants like moss, orchids, succulents, cacti, and bonsai trees

8. Size: 5-8cm

9. Weight: 500g