Check the listing for details. Seachem Matrix Carbon High Efficiency Carbon Optimum Hydrodynamics 250ml. Color: Blue, Condition: New, Made in US. Listed at 16.12 USD. Matrix Carbon is a truly unique activated carbon. It is formed as a spherical bead for optimum hydrodynamics, and will not pack. It permits maximum water flow and contact with its high density of microporous binding sites. Matrix Carbon has a very low ash content as indicated by its minimal impact on ph. Even when added to distilled water, it does not raise pH above 7.0. While all carbons contain phosphate, regardless of false claims to the contrary, Matrix Carbon has the lowest detectable leachable phosphate content of all major carbon brands tested. Matrix Carbon outperforms other high grade carbons by at least two-fold when compared for total capacity to remove aquarium organic matter, rate of adsorption, and duration of use.