NOVELTY - A biofilter system (100) comprising a main biofilter chamber (110) having inlet and outlet ports (104, 106) and containing aerobic and anaerobic bacteria (102, 108) without physical separation; and mechanism for oxygenating the aerobic and anaerobic bacteria in the main biofilter chamber having mechanism for timing the oxygenation (112) of the aerobic and anaerobic bacteria, is new.    USE - The biofilter system is used for removal of carbonaceous matter and/or nitrogen matter from animal waste by contacting in a biofilter chamber the aqueous source with aerobic and/or anaerobic bacteria, providing high-oxygen conditions, providing anoxic conditions, alternating periodically the conditions of the biofilter chamber, and monitoring an outflow from the biofilter chamber for predetermined levels of carbonaceous matter and/or nitrogen nitrogeneous matter (claimed).    ADVANTAGE - The invented biofilter system is efficient and inexpensive in biological treatment of aqueous waste and raw animal waste.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are also included for:    (1) an aquaculture system comprising an aqueous environment, mechanism for fluidly connecting the aqueous environment with the biofilter system, mechanism for disinfecting an outflow of the biofilter system, and a mechanism for returning the disinfected outflow to the aqueous environment;    (2) aquaculture comprising growing fish in the aqueous environment; and    (3) a system for treating animal waste comprising a first vessel having a first inlet and outlet ports and mechanism for degrading animal waste solids within the animal waste and mechanism for separating animal waste solids and animal waste liquid (116), and a second vessel comprising the biofilter system.    DESCRIPTION OF DRAWING(S) - The figure is a schematic representation of a biofilter system.    Biofilter system (100)    Bacteria (102)    Inlet and outlet ports (104, 106)    Main biofilter chamber (110)    Oxygenation (112)    Waste liquid (116).