Effects of porous concrete block and phosphorus absorbent on water quality purification of a pond are investigated. The pond of the interest is of 40m^3 in water storage capacity and 160 cm in depth. Volumetric rates of the water purification materials of the blocks and the absorbents to the pond capacity are 2.5% and 1.2%, respectively. To make it possible for the whole body of water to contact the materials, the pond water is circulated with a pump of 80L/min. As a result, the degree of transparency of the water in the pond has remained more than 160 cm for more than six years. Concentrations of total phosphorus (TP) and total nitrogen (TN) have been in the range of a detection minimum (<0.003mg/L) to 0.026mg/L and a detection minimum (<0.2mg/L) to 4.7mg/L, respectively. Loads of TP and TN to the pond from the external sources such as tap water, rain and fallen leaves are 48g/year and 5,300g/year, respectively, while their removals from the pond, including by sediment removals from the phosphorus absorbent tank, are 24g/year and 1,800g/year, respectively. The difference in TP between the amount of loads and removals is roughly identified with 20g/year of the accumulation amount that could be calculated from the distribution of TP in the pond. However, the difference in TN, 3500g/year, deviates from 300 g/year estimated from its distribution. This disparity is considered to balance with the nitrogen loss resulting from denitrification.