<;P>;PROBLEM TO BE SOLVED: To provide artificially rearing water suitable for rearing both freshwater fishes and saltwater fishes, instead of natural seawater. <;P>;SOLUTION: This artificially rearing water used for artificially rearing seawater organisms and freshwater organisms is characterized by adding sodium, calcium, and potassium to rearing water to give a specific gravity of &ge;1.004 and equal to or less than that of natural seawater, a potassium/calcium existence ratio of 0.93 to the existence ratio in the natural seawater, and a sodium/(calcium+potassium) existence ratio of 55 to the existence ratio in the natural seawater. <;P>;COPYRIGHT: (C)2010,JPO&INPIT