Abstract: An aquarium water treatment device for treatment aquarium water includes a housing that has a top and a bottom. A partition is frictionally coupled to a wall of the housing proximate to the bottom, defining a lower chamber and an upper chamber. A plurality of penetrations is positioned in the partition. A pump that is submersible has an intake, positionable in an aquarium, and an outflow that is fluidically connected to the lower chamber. The pump is configured to transfer water requiring treatment from the aquarium to the lower chamber. A coagulation promoter and a flocculation promoter can be added as required to the housing such that solids in the water are induced to form a sludge bed above and below the partition. A nozzle is positioned proximate to the top and fluidically connected to the upper chamber so that clarified water flows back into the aquarium.