Abstract: External filter assembly for aquariums includes a filter chamber containing a mechanical and/or chemical filter and a functionally active filter upstream of the mechanical filter for actively filtering the water before the water is filtered by the mechanical filter. Fresh air is mixed with the aquarium water immediately upstream of the functionally active filter whereby the functionally active filter is directly exposed to both dissolved oxygen in the water and atmospheric oxygen mixed in the water which significantly improves both the efficiency and capacity of the filter in performing its active function. Both the mechanical/chemical filter and the functionally active filter are cartridge type filters, whereby either may be replaced without disturbing and/or affecting the operation of the other.

Abstract: A foam fractionation protein skimmer assembly/apparatus for removing organic waste material from water within an aquarium includes a foam fractionation column adapted to be partially submerged in the water in an aquarium and an aerating water pump which mixes air with water drawn from the aquarium internally within the pump and pumps the aerated water into the column through an external water intake port on the column to provide a downward flow of water in the column counter to air bubbles rising within the column to induce production of surfactant-containing foam on the surface of the water within the column. The column itself is comprised of a plurality of separate tube sections or chambers frictionally connected together for ease of assembly and disassembly to facilitate cleaning of the column.

Abstract: A water filtration system includes an auxiliary filter assembly having a single inlet connected to the water lift tube of an undergravel filter and an outlet connected to a submersible electric water pump which causes the water within an aquarium to flow through both the undergravel filter and auxiliary filter assembly before being recirculated back into the aquarium.