The swiveling pump head and multi-stage filtration are the standout features of the EHEIM Biopower 200, which benefits from the aquaball concept. What is particularly special about this Biopower is that it offers multi-stage filtration similar to that of an external filter. The closed filter baskets are filled with highly efficient filter media, such as SubstratPro. At the bottom is the intake basket with a filter cartridge for mechanical-biological pre-filtration. The water drawn in from below is pumped through the various filter layers and ultimately returned cleaned to the aquarium.