Matrix is a high porosity biomedia that provides efficient biofiltration for the removal of nitrogenous waste. Matrix is a porous inorganic solid about 10 mm in diameter. Each litre of Matrix provides as much surface (>~700 m2) as 170 litres of plastic balls! Plastic bio-materials provide only external surface area, whereas Matrix provides both external and internal macroporous surface area. These macropores are ideally sized for the support of nitrifying and denitrifying bacteria. This allows Matrix, unlike other forms of biomedia, to remove nitrate along with ammonia and nitrite, simultaneously and in the same filter. Matrix is completely inert and will not breakdown. It need not be replaced. Since the majority of the bacteria are internal, Matrix may be rinsed when needed without damaging the filter. Matrix is compatible with all types of wet or wet-dry filters.