Meridianâ„¢ is an all natural oolitic (spherical or egg shaped) aragonite substrate for all reef and marine aquaria. Meridianâ„¢ is the premium aragonite substrate for the reef aquaria. It's grain size (a fairly uniform 0.25 - 0.50 mm) is ideally suited to reef inhabitants and it's chemical composition will assist in stabilizing calcium and alkalinity while preventing large pH declines. Unlike competing "wet" products marketed under the guise of being "live", Meridianâ„¢ is sold dry, thus you pay only for gravel and not for unneeded water. 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 aquarium cycle time for a new system, then the use of a product designed for that particular purpose would be more appropriate (such as Seachemâ€™s StabilityÂ®).