Filter for aquariums

A filter for aquariums with filter cartridge and ajoining head is proposed, which in the housing contains a self-starting synchronous motor with permanently magnetised rotor and a pump impeller seated directly on the rotor shaft in a pump chamber, the radial outlet of which, lying on a circumferential side, is seated at the lower head end and opens into a pressure duct leading to the upper head end. Between the base plate and the pump chamber is a control wheel, rotatably adjustable by hand, for regulating the rate of flow. This has an axially through-extending control window with an adjoining radial duct, which is axially covered by the base plate, and towards the centre is connected to the axial suction side of the pump by way of coincident wall breaches in the tubular part of the control disc and pipe connections of the base plate engaging therein, depending on the rotational position of the control disc.