lava stone Size: 0mm - 300 mm Colour:black, red Feature:No radiation,no poisonous and no odor etc. Product DescriptionVolcanic rock filter media(F02), Filter media in water treatment Volcanic rock filter media(F02) advantage: Volcanic rock makes and excellent biological and mechanical filter media High poros Ideal for biofall, barrel and similar pond filters Ideal for wet/dry and canister ...