Undergravel fishtank filter

Claim 1

An undergravel fishtank filter comprising an inlet conduit for disposition below gravel in a fishtank, a chamber in communication with the inlet conduit and housing filter means in the form of a removable cartridge, a convergent nozzle extending upwardly from the chamber and having an elongated rectangular horizontal cross-section, a lower end of the convergent nozzle being connected to the chamber and the upper end being of smaller cross-section than the lower end, an air bubble dispensing device disposed at or adjacent to the lower end of the convergent nozzle, the air bubble dispensing device comprising a rectilinear apertured tube extending along or parallel to the longitudinal extent of the lower end of the convergent nozzle, wherein the convergent nozzle comprises a fixed front wall and two fixed end walls projecting upwardly from the chamber, a rear wall pivotably mounted for opening and closing movement about an axis extending parallel to the longitudinal extent of the lower end of the convergent nozzle to allow removal of the cartridge through the nozzle, two arcuate slots being formed respectively in the end walls, and the apertured tube being attached to the rear wall and extending through the two arcuate slots.