Water is one of the most important constituents of environment for life. In the class of environmental education at school, children often think about purification of the polluted water in lakes and rivers. However, children may not have enough time to consider what is clean or healthy water for life. They sometimes confuse biologically polluted water with chemically polluted one. The present paper shows that the clean water good for human being is not always good for other organisms. We investigated here the possibility of natural mineral waters on the market as teaching materials for environmental education. The result obtained are followings. (1)There are different qualitatively and quantitatively in their chemical components among the natural mineral waters those are good to drink on the market. Children can learn that the differences in chemical components reflect the geology. (2)The microorganism such as Volvox is very sensitive to the quality of the water. We cannot keep it alive for long time in distilled or ultra―pure water. The microorganism can be alive in some balanced salt solutions. Volvox lived and grew in some mineral waters but not in others provably because of the high concentration of Mg2+ and Ca2+. (3)Moreover, the relationship between growth of microorganisms and quality of water is available to learn the roles of soil, for example, source of supply of mineral required for its growth.