Gray Coast™ Calcite is an all natural substrate for all types of marine, reef and tropical aquaria. Simply rinse before use to remove any residual dust. To determine the number of bags required for your aquarium, please note that each bag (10 kg, 22 lbs) occupies a volume of 6000 cm3 (0.21 cu. ft.). To determine your desired volume multiply tank width by length by desired depth. How do calcite and aragonite compare? While calcite and aragonite share the exact same chemical composition, aragonite has always been favored for marine aquaria because of its higher buffer capacity. However, magnesian calcite, such as our Gray Coast™, has been shown to have a higher buffer capacity than even aragonite, making it an ideal choice for marine aquaria.