Exo Terra® Bio Drain is a natural inorganic material that allows excellent drainage in the terrarium. It will not rot or decompose like other natural materials. The optional Exo Terra® Drainage Mesh will help keep the Bio Drain material separate from the decorative top layer of the terrarium, preventing the mixing of different materials and water contamination. The Bio Drain material will function as a biological filtration system. Clean water can then be circulated in waterfalls, the Exo Terra® Rain System, or hanging plants. Use Bio Clean (formerly known as Biotize) to accelerate biological filtration capabilities.