Abstract: An aerator for an aquarium has a connector for connecting the aerator to an existing filter system. An air receiving and dispensing chamber is annular and defined between a lower annulus and an upper perforate annulus. Walls on the lower annulus mate with skirts on the upper, perforate annulus to define inner and outer walls of the chamber. Water flows through the central openings in the annuluses, from the filter, upwardly, and air passes through the upper, perforate annulus. A mixing chamber is received over the upper, perforate annulus, and a tube can be connected to the mixing chamber to carry the aerated water up. An air supply tube extends down through the center of the aerator and connects to the chamber to supply air to the chamber.

Abstract: An inside multi-functional sponge filter for an aquarium tank is described which consists of a vertical cyclindrical sponge filtering medium surrounding two interchangeable cylindrical components which functions as the clean water receiving chamber in which an optional filter medium cartridge can be added. The outer diameter of the sponge is cut with shallow rectangular grooves oriented along the longitudinal axis. The longitudinally oriented slots about the circumference which provide for maximum decontaminated fluid flow rates into the chamber. The two cylindrical components are fitted with other filter sections via male/female connections constructed as part of the component. The lower cylinder is attached to a weighted cylindrical flanged base to prevent floatation.