There are two types of filtration action in every bio-filter. First is mechanical filtration. At the top of each filter is a foam set, these foams physically strain the water removing particles of fish waste and debris from the water. The second type of filtration i s biological, below the foam sets are bio-media called Flcor (or Bio balls). The purpose of this media is to allow helpful bacteria to grow on it's surface. The bacteria absorbs the pollutants within the pond water and neutralise ammonia and nitrite deposits then recycles the pollutants to nitrate which is a natural plant food.
