Check the listing for details. Eheim Substrat 1L Aquarium Filter Media Fish Tank Bio-Filter Medium Reusable. Condition: New. Listed at 32.95 USD. EHEIM SUBSTRAT Made in Germany, this is new, old stock with shelf ware. Substrat is in factory seal package. Standard bio-filter medium with large colonisation area for bacteria cultures and 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 and marine water, is washable and can be reused.Standard bio-filter mediumHighly porous material made from sintered glassExcellent conditions for bacteria culturesReusable (rinse carefully to clean)Suitable for fresh and marine waterTip:Never clean or change all the filter media together in one operation (and never clean too rigorously). The bacteria cultures must not be completely destroyed, otherwise re-colonisation will be retarded. The filter baskets in the external filters and filter modules in the internal filters aquaball an biopower are ideal for partial cleaning. Biological Filter MediaThe main task of biological filter media is to offer the best colonisation conditions for the bacteria cultures, so that after a short time a bacteria lawn develops. The bacteria feed on dirt particles of all kind and convert substances critical for the aquarium. After the first cleaning process by the mechanical filter media (e.g. EHEIM MECH or MECHpro) the biological filtration is the most important. It provides for clear, healthy water and stabile water values. That’s why we have invested a lot of research work into the development of biological filter media.