Gray Coast™ Calcite is an all natural calcite substrate for all types of marine, reef and tropical aquaria. Its chemical composition will assist in stabilizing calcium and alkalinity while preventing large pH declines. Unlike competing “wet” gravels, Gray Coast™ is sold dry: this bag contains 35% more gravel than a bag of wet gravel of equal weight. These products imply that they contain living, microscopic animals when in fact they only contain common bacteria. Dry or wet, there are bacteria on every substrate available. If one is concerned with shortening the tank cycle time for a new system, then the use of a product designed for that particular purpose would be more appropriate (such as Seachem'sStability®).