Description Flourite Dark 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 freshwater 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. Flourite Dark is good for the life of the aquarium and need not be replaced. To determine the number of bags required for your aquarium, please note that each bag (7 kg, 15.4 lbs) occupies a volume of approximately 5,500 cm3 (325 cu. in.). To determine your desired volume multiply tank width by length by desired depth. Directions Although it is pre-washed, because Flourite Dark is a natural product, it may become dusty in transit and require rinsing before use to remove any residual dust. NOTE: The specialized mesh bottom of the 3.5 kg size allows it to be rinsed right in the bag.