Seachem Pond Matrix Seachem Pond Matrix is a high porosity biomedia that provides efficient biofiltration for the removal of nitrogenous waste in ponds. Plastic bio-materials provide only external surface area, whereas it provides 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. It is completely inert and will not breakdown. It need not be replaced. It is also more suitable for use as a clean soil replacement for growing pond plants. Use 1–2 Liters of Seachem Pond Matrix for each 100 US gallons. Since the majority of the bacteria are internal, it may be rinsed when needed without damaging the filter. Matrix is compatible with all types of wet or wet-dry filters. View our other Seachem items here.