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