Abstract: A cleaning device for cleaning the back side of a panel with a control member and a cleaning member, which is separate from the control member and which has a base member and two blades disposed thereon. The control member and the cleaning member interact magnetically through the panel, so that the cleaning member disposed on the back side of the panel can be guided along the panel while pressing the cleaning edges of both blades on the back side of the panel by means of the control member disposed in a manner corresponding to it on the front side of the panel. The two blades may be of different lengths and, by suitable geometry and arrangement of the blades or of magnetic elements, the shorter of the two blades exerts a greater pressing force on the panel with its cleaning edge than does the longer.

Abstract: In order to generate waves in a volume of water of an aquarium, it is proposed that a storage container which extends beyond the surface of the volume of water should be provided in the aquarium. Using a pump, water is periodically pumped from the water container into the storage container and returned from the storage container into the aquarium. The energy delivered to the water during this leads to fluctuations in the position of the free surface of the volume of water and in-phase operation of the pump provides stronger surface displacements in the aquarium, which are comparable with a wave in open water and which expose the plants and living beings in the aquarium to an alternating mechanical load.

Abstract: It is proposed to avoid an excessive formation of foam in the collection vessel of a protein separator by throttling the feed of air to a foam generator according to the foam generation rate in the separator. The foam generation rate in the separator can be measured by the amount of phase water that is separated in a second separator, which is located between the foam collection vessel and a first separator, in which second separator the mixture generated by the foam generator is freed from liquid constituents.

Abstract: A magnet-holder for attaching an object to a glass pane has two parts of a holder which can be placed on mutually opposed boundary faces of said glass pane and are biased towards one another by a magnetic-force apparatus. In addition, that part of the holder which is disposed on the inner side of the glass pane has a contact plate whose side that faces towards the glass pane carries a plurality of elastic holding cups which can cling to the pane.

Abstract: In order to generate waves in a volume of water of an aquarium, it is proposed that a storage container which extends beyond the surface of the volume of water should be provided in the aquarium. Using a pump, water is periodically pumped from the water container into the storage container and returned from the storage container into the aquarium. The energy delivered to the water during this leads to fluctuations in the position of the free surface of the volume of water and in-phase operation of the pump provides stronger surface displacements in the aquarium, which are comparable with a wave in open water and which expose the plants and living beings in the aquarium to an alternating mechanical load.

Abstract: In order to generate waves in a volume of water (12) of an aquarium, it is proposed that a storage container (22) which extends beyond the surface of the volume of water (12) should be provided in the aquarium (10). Using a pump (32), water is periodically pumped from the water container (10) into the storage container (22) and returned from the storage container (23) into the aquarium (10). The energy delivered to the water during this leads to fluctuations in the position of the free surface (14) of the volume of water (12) and in-phase operation of the pump (32) provides stronger surface displacements in the aquarium (10), which are comparable with a wave in open water and which expose the plants and living beings in the aquarium to an alternating mechanical load.

Abstract: In a propeller pump for an aquarium, starting-up of the rotor in the correct direction of rotation is guaranteed through the fact that a unit, which is formed by the propeller and the rotor of the pump, is disposed on a spindle in an axially displaceable and rotatable manner. If starting-up occurs in the wrong direction, said unit, and thereby the rotor, is drawn axially out of the magnetic field of the stator until the magnetic coupling between said stator and said rotor is no longer sufficient for further driving in the angular direction. The unit formed by the rotor and the propeller is then drawn back into the stator again by axial magnetic components of force, where a fresh opportunity of starting up again is imparted to it. It is guaranteed that the rotor will revolve in the correct direction after, at the latest, a few attempts at starting up.

Abstract: A magnet-holder for attaching an object to a glass pane has two parts of a holder which can be placed on mutually opposed boundary faces of said glass pane and are biased towards one another by a magnetic-force apparatus. In addition, that part of the holder which is disposed on the inner side of the glass pane has a contact plate whose side that faces towards the glass pane carries a plurality of elastic holding cups which can cling to the pane.

Abstract: In order to generate waves in a volume of water (12) of an aquarium, it is proposed that a storage container (22) which extends beyond the surface of the volume of water (12) should be provided in the aquarium (10). Using a pump (32), water is periodically pumped from the water container (10) into the storage container (22) and returned from the storage container (23) into the aquarium (10). The energy delivered to the water during this leads to fluctuations in the position of the free surface (14) of the volume of water (12) and in-phase operation of the pump (32) provides stronger surface displacements in the aquarium (10), which are comparable with a wave in open water and which expose the plants and living beings in the aquarium to an alternating mechanical load.