The examination for water quality of salty groundwater pumped up from a depth of about 50 m located on the campus of the School of Marine Science and Technology, Tokai University, Shizuoka, Japan was implemented from August 2003 to December 2004, for the purpose of clarifying the merit and demerit of the water concerned when it is applied to aquaculture. The groundwater pumped up has good qualities in terms of a salinity as similar to seawater, an almost constant temperature of around 20°C, a constant pH value and highly nutritious. However, its disadvantage is that ammonium and manganese, which are toxic to the growth of fishery flora and fauna, are in high amounts. To alleviate those major constraints caused by both the ammonium and manganese ions, an enhancement measure has been established by installing an oxidation tank, which acts as a facilitator to achieve oxidation for ammonium and manganese ions, being made of specified microbes. It has successfully reduced those hazardous ions to a level favorable to aquaculture. Carbon fibers were used as a substrate for the bacteria growth and also for the precipitation of the substances. Finally, the aquaculture business on land can be developed better by utilizing the results obtained through the current study.