抄録
Productivity of fish culture ponds decreases with the lapse of time owing to accumulation of waste materials and excrements. It is necessary to remove the filth for maintenance of the normal productivity of a pond. This experiment has been carried out in the ponds of Fisheries Training Center at Nagano Prefecture in December, 1961 and February, 1962, to determine the cleaning capacity of the so-celled fish pump. The results obtained are as follows:
The underwater type pump is suitable for pond cleaning because this type is easy to operate. Pumps with 4-inch or lessin caliber are fit for use in the present fish culture ponds. Generally, the nozzle of suction hose should be attached on to the bottom of pond vertically in operations. The shape of nozzle must be changed depending on the difference of bottom materials.
