EHEIM SUBSTRAT 1 Litre Standard bio-filter medium with large colonisation area for bacteria cultures & high efficiency SUBSTRAT can be layered in one or more layers. It is a highly porous filter material made from sintered glass. The surface structure offers the important purification bacteria excellent colonisation conditions. The colonisable area amounts to 450 m² per litre.EHEIM SUBSTRAT is suitable for fresh & marine water, is washable & can be reused. Standard bio-filter medium Highly porous material made from sintered glass Excellent conditions for bacteria cultures Reusable (rinse carefully to clean) Suitable for fresh & marine water