Filter cartridges for mechanical and biological filtration. Dirt particles are trapped in the porous foam. At the same time, the material offers a large colonisation area for cleaning bacteria. After only a short running-in period, the foam cartridges ensure not only mechanical water clarification but also biological pollutant decomposition. The cartridges can be used several times. For cleaning, they should only be rinsed and squeezed out so that the bacteria cultures are not completely destroyed.