Sponge filters offer biological and mechanical filtering: they represent the ideal surface for bacteria to settle, and the sponge catches coarser dirt particles for clean water without any danger for larvae of fish Double filter sponge: the biological filter function takes effect quickly, and the oxygen content also increases; Ideal filtering thanks to a mechanical and bioactive working method High quality foam, large surface area, i.e. no dissolution in water and no toxicity The foam structure (open pores) is retained even after prolonged use
