Seachem Flourite Black is a substrate of the highest quality. Composed of specially fracted stable porous clay gravel designed specifically for use in natural planted aquariums. The mineral-rich gravel is an attractive deep black colour that is not chemically treated or coated and will not alter the delicate pH balances within the tank. The gravel is most effective when used on its own, but it may also be mixed with other types of substrates without any negative reaction. Gravel modifiers such as laterite are not necessary for the success of this gravel