Flourite Black Sand� is a specially fracted, stable porous clay gravel for the natural planted aquarium. Its appearance is best suited to planted aquaria, but may be used in any aquarium environment. Flourite Black 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. Flourite Black Sand� is not chemically coated or treated and will not alter the pH of the water.