The Exo Terra Sub Stratum is collected from the mineral-rich foothills of the Aso Volcano in Japan. The natural volcanic soil, formed from andesitic and rhyolitic tephra, is very nutrient rich, ideal for lush plant growth in bioactive planted terrariums.  The porous surface allows for excellent drainage and aeration, supporting strong root growth. The Sub Stratum’s friable, low density structure promotes a flourishing population of beneficial, nitrifying bacteria, creating a self-sustaining, living terrarium ecosystem. The active beneficial bacteria of the soil will decompose biological waste, keeping the terrarium clean and healthy.