Packing material unit used for biological treatment of water in fish- and garden ponds, comprises inner porous body surrounded by open-pore outer body

摘要

The inner porous body (10) is surrounded by an open-pore outer body (20) made of a second material. The first material has a pore size of 10-100 mu m, preferably 20-60 mu m. It is a silicate. The second material porosity is 10-45 ppi. It is a foam. Both sections are tubular, the second gripping around the first. The first tube section has an outer diameter of 15-32 and wall thickness 2-10 mm. The second has wall thickness 30-70 mm. The length of the second tube section exceeds that of the first.