Acorus calamus

Calamus, as mentioned, is often used in a so-called plant filter or helophyte filter. Such a filter involves pond water flowing past the roots. The extensive root systems of the helophytes harbour a huge number of bacteria. These bacteria break down the nutrients in the water so that the plants can use these dissolved nutrients for their growth. The bacteria have a symbiotic relationship with the helophytes. Installing a plant filter or helophyte filter ensures that too few nutrients remain for algae, preventing them from growing properly. A helophyte filter is also very suitable for use in swimming ponds or koi ponds, as not many plants are needed in the pond itself.