Seachem Onyx Sand is a naturally dark gray sand that perfectly complements and enhances the appearance of any aquarium. It supports optimal KH levels for freshwater planted aquariums. Although ideally suited to planted aquaria, it may be used in any aquarium environment. Seachem Onyx Sand is most effective when used alone as an integral substrate bed, but it may be mixed with other gravels. Gravel modifiers such as laterite are not necessary. Seachem Onyx Sand is not chemically coated or treated, and as a carbonate rich sand, it has a slight buffering capacity that may raise pH by 0.1 - 0.5 pH units (depending on source water characteristics). Seachem Onyx Sand is good for the life of the aquarium and need not be replaced.Use of Seachem Onyx SandAlthough it is pre-washed, because Seachem Onyx Sand is a natural product, it may become dusty in transit and require rinsing before use to remove any residual dust.When adding water to aquarium, fill slowly to avoid disturbing Seachem Onyx San