Create decorative water drainage systems without contamination from decorative substrate particles with the Exo Terra Bio Drain Terrarium Draining Reptile Substrate. The Exo Terra BioDrain Terrarium Draining Mesh is part of the BioDrain Terrarium Draining System. This non-toxic mesh keeps the underlying draining substrate separate from the decorative terrarium top-layer substrate which allows proper water drainage and prevents contamination. It is ideal for creating water areas and biological filtration systems. Exo Terra Terrarium Moss, Jungle Earth or Plantation Soil can be used as decorative substrates.