The Exo Terra BioDrain Terrarium Draining Mesh is part of the BioDrain Terrarium Draining System. The non-toxic mesh will keep the underlying Draining Substrate separated from the decorative terrarium top-layer substrate. It also allows proper water drainage when used in combination with the BioDrain Terrarium Draining Substrate, as the BioDrain Terrarium Draining Mesh prevents contamination of the water by decorative substrate particles. It is ideal to create water parts and a biological filtration system in the terrarium using the Exo Terra BioDrain Terrarium Draining Substrate. The clean terrarium water can then be circulated in waterfalls, the Exo Terra Rain System or Dripping Plants. Use Bio Clean (formerly known as Biotize) to speed up biological filtration capabilities. As a decorative terrarium substrate the Exo Terra Terrarium Moss, Jungle Earth or Plantation Soil, etc. can be used. Key Features : Non-toxic non-decomposable liner Create a water drainage system Separates the BioDrain Terrarium Draining Substrate from decorative substrates Prevents substrates from contaminating the water Other Sizes Available : 3131 Mini 30 x 30 cm 12in x 12in 3132 Small 45 x 45 cm 18in x 18in 3133 Medium 45 x 60 cm 18in x 24in,