High-performance filter medium for mechanical filtration. The innovative, patented 3D structure of the sera crystal clear Professional fibers quickly removes even the smallest particles larger than 10μm (such as floating algae or sludge). Unlike common filters, the filter balls retain their shape and can be washed several times. They are 80% reusable after washing. The high-performance filter medium is suitable for both freshwater and saltwater aquariums and all types of filters. The sera siporax Professional biological filter is the perfect addition to the sera crystal clear Professional.