Fluval Bio Stratum – Made from 100% natural, mineral-rich volcanic soil from Mount Aso in Japan and infused with beneficial nitrifying bacteria, Bio-Stratum is specifically formulated to provide immediate biological activity and maintain ideal conditions for a thriving planted aquarium. Characterized by its non-compacting 1 mm powder granules, Bio-Stratum allows plants with even the finest and most delicate roots to easily spread throughout the porous substrate while absorbing a powerful mix of nutrients, minerals, and trace elements that promote explosive growth and overall health.