Shirakura White Mineral Stone is comprised of an interesting substance called Montmorillonite.
Montmorillonite is a very soft phyllosilicate group of minerals that typically form in microscopic crystals, forming a clay. It is named after Montmorillon in France, and is derived from geologic tectonic plate activity, volcanic action and river hydrolysis. Montmorillonite silicate attracts valuble mineral nutrients from mountain soils and streams. Montmorillonite is effective as an adsorptive of heavy metals in water, and will attract and bind ammonia, nitrite, methane, and other metabolic waste products in the aquarium water.
ShirakuraWhite Mineral Stone is a useful addition to a shrimp aquarium, as it will swell and slowly dissolve into the water column, providing trace minerals necessary for coloration and health of ornamental shrimp, such as Silicon, which helps build and maintain the exoskeleton, Magnesium, which helps their digestive system, and Calcium, which helps maintain the integrity of their shell.
Like any other natural product, the results you can achieve are varied. You need to observe good overall husbandry and common sense. There are no "miraculous" results that you can expect from this stuff, despite some of the attributes that have been ascribed to it by many. If employed as another "tool" in your "toolkit" of husbandry and techniques, this product can certainly provide some positive benefits for your aquatic environment.
Shirakura White Mineral Stones begin to function when they are saturated with water. Immerse them in water for about 30 minutes before adding them to the aquarium. This will prevent them from cracking and breaking. The recommended quantity is 100 grams of stone for every 13-18 gallons (50-70 liters) of aquarium capacity. Replacement is advised after approximately 4-6 months.