This substrate is both mineralogically and biologically complete. It is ready to use, no rinsing required and is water packed in conditioning solutions geared specifically for this eco-system. It will not only maintain chemical water parameters, but the live bacteria allows for safe and rapid cycling as well. Mineralogically complete because it contains Aragonite that helps to maintain the high pH African Cichlids need without the constant addition of chemicals; buffers automatically for the life of the aquarium; adds calcium, magnesium, carbonate and more; the dark color encourages the richest coloration in fish; the unique composition re-creates the African Rift Lake environment; it has a high initernal porosity for maximum carrying capacity-keep more fish healther-- longer. Biolocigally complete because it contains live water-purifying bacteria that makes cycling a new aquarium faster and safer; you would have to buy 4 bags of ordinary gravel to equal the surface area available for water purifying bacteria in 20 pounds of this product; it creates a natural biological balance to discourage nuisance algae. Typical Size: 0.5 - 1.5mm