MatrixCarbonª 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 macroporous binding sites. MatrixCarbonª 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, MatrixCarbonª has the lowest detectable leachable phosphate content of all major carbon brands tested. MatrixCarbonª 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. This product is sold by volume. Cited weight is minimal weight.