Siporax™ Biomedia A high-performance, fine-pore biofilter media with unbelievably high surface area (82,000 ft2/ft3) and the ability to perform both nitrification and denitrification under certain conditions. Siporax™ works best with well-filtered, clear water (otherwise heterotrophic bacteria will cover the surface). Sold in one-liter mesh bags. Made in Germany.