| 摘要 |
It has been known that water having a pH value of 5.5 to 7.5 is suited for the rearing of fresh-water fish and hydroponic cultivation of plants. Bottom soils or filtering media prepared by mixing carbonates of alkali metals or alkali-earth metals with volcano-ash-base soils and sintering the mixture into granules. When used in water tanks or reservoirs for fish rearing or hydroponic cultivation, the bottom soils or filtering media thus prepared provide favorable environments for such rearing and cultivation. |
