A completely convincing concept. The spherical pump head is mounted in a ball joint and can be rotated in all directions. This allows the outflow of purified water to be directed in any direction. The pump performance and flow rate are adjusted using the rotary knob on the outlet nozzle. The included power diffuser regulates the air supply and thus the oxygen enrichment in the aquarium. Directly beneath the pump head is the media box, which can be filled with a filter mat for mechanical-biological filtration, a filter fleece for fine filtration, bioMech or Substratpro for biological filtration, or Eheim Aktiv for adsorptive filtration. Additionally, in the other filter modules, both biologically and adsorptively functioning filter cartridges or filter sponges can be used. Aquaball is modular in design, meaning that by adding or removing filter modules (filter containers), the filter volume can be individually adjusted to the aquarium. For expansion, there is the Expansion Set 2; the filter containers are simply clipped together or apart (Easy-Click closure system). Due to the modular design, the filter cartridges or media can be cleaned at staggered intervals, preserving the bacterial cultures. Aquaball draws in water over a large area. The round filter modules are designed so that the aquarium water is evenly absorbed from all sides over almost the entire outer surface. The holder for Aquaball is easily attached to the tank with suction cups. For cleaning, replacing parts, or filling filter media, the filter can simply be removed from the holder.