<；P>；PROBLEM TO BE SOLVED: To provide a magnesium-based slow-dissolving agent which dissolves in an aqueous solution gradually over a long period of time, can easily be handled because of improved hardness and is effective for neutralization treatment of detergent drain or the like and nutritional support for cultured fish and shellfish. <；P>；SOLUTION: The slow-dissolving agent is prepared by preserving a granule 1 which contains calcium components and has inorganic magnesium compounds as a main ingredient in the atmosphere filled with a carbon dioxide gas. The dissolution rate of the granule after preservation is further slower than that before preservation. <；P>；COPYRIGHT: (C)2008,JPO&INPIT
