The Eheim professionel II external filter has an integrated, maintenance free pump that provides constant circulation of aquarium water that is treated mechanically, biologically or by adsorptive means depending on the media used. Aquarium water is directed to the bottom of the filter first then up through the various media layers until filtered water is returned to the tank. Mfg. Note: Optimum filter performance & problem free operation is achieved only when original Eheim filter media are used.
Thanks to the ingenious "push II prime" pump head, the new Pro II filters