Home fish-tank filter construction

A filter housing is connected to a water pump located at the bottom of the housing such that water can be sucked from the fish-tank directly into the pump, to then be expelled from the pump and forced to flow upwardly through a first filter chamber; an overflow partition separates the first filter chamber from a plurality, typically two further filter chambers, the further filter chambers being alternately interconnected at the bottom by communicating openings, or by overflow partitions, the last chamber in the filter construction being arranged to have water rising to the top level within the filter structure, and a slanting downwardly directed trough is connected to the last overflow so that water will flow by gravity freely back into the fish-tank or aquarium. The final chamber in the filter structure may include a heating element, the overflow being hook-shaped to simultaneously form an attachment of the filter structure to the fish-tank.