Replacement foam set BioPress 4000 INT

For BioPress Set 4000. The heart of a filter is its filter sponges – especially this filter sponge set, which combines the blue and black sponges in a compact space. Black filter sponges have the finest filtration properties, while the blue ones have coarser ones. This means that, depending on the water flow rate, either the smallest or only larger particles get trapped in the sponges and are thus removed from the pond water. But they don't just perform classic filtration; they also provide ample habitat for bacteria. This small biological oasis in the filter sponges ensures the conversion of toxins produced in the pond: In the blue sponges, toxic substances are converted into harmless, but algae-stimulating substances (nitrification), which in turn are converted into naturally occurring gases in the black sponges (denitrification).