Breeding tanks are circular in shape as in Chinese hatchery system. A convenient size of a breeding tank is 2m diameter and 1 meter deep which would hold about 1800 liters of water. To impart a circular motion to water, sideways-directed inlets are installed towards the bottom end of hatching wall. The rate of flow of water in a 1800 liters circular tank may be 6-8 liters/sec. The other components of a circular breeding tank are socket to cover the centrally drain hole into which would fit a uniformly perforated straight pipe and screen covering the perforations. The non-metal screen is to prevent eggs from escaping through the outlet. The other part of the Chinese hatchery system consist of egg collection chamber, hatching tanks, and hatching collection chamber. It is an open system wherein temperature is not controlled.
A combination of ground water and canal water or pond water are used. Gravitational force is normally used for the eggs to get into the hatching cistern where in continuous circulation of water is maintained. The Chinese hatchery system is meant for incubating very high density of eggs i.e. 7,00,000–12,00,000 eggs per cubic meter and provided with running water. This consists of hatching trough/cistern with filtering screen, nozzles, water inlet and outlet valve and fry collecting compartment.
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