The system consists of a unit of breeding tanks of metal, cement or plastic pools with cooling tower or air conditioners to control the water temperature and a slow continuous flow of water may or may not be maintained. The water may be filtered by means of an in-situ filter and a pump is used to pump in water to the storage tank. Aeration facilities with an air blower or compressor, vertical hatchery jars made of glass, galvanized iron sheets or polythelene, water supply system from the storage tank to the hatching jars and spawnery or hatchling storage tanks are the components of this type of hatchery. In a jar hatchery of Indian hatchery system, the water inlet can be from below (or) above but the exit is always at the top.
The design of the jar would depend upon which type of inlet is chosen. Ordinarily, however, hatchery jars with water supply from below are more commonly used. The hatchery jars with water supply from below can be of diverse volumes and shapes. The shape may vary from plain cylindrical contour to a funnel, conical (or) barrel shape. The material may vary from one liter to 200 liters. A 10 liter jar has the capacity to hold 100,000 water hardened swollen carp eggs and a rate of flow of water is maintained at 600–800 ml per minute for Indian major carps and 800–1000 ml for silver carp and grass carp. In hatching jars of higher capacity more eggs can be introduced but the flow of water has to be suitably increased. The hatching time inside the hatchery is nearly 2–3 hours less than in the field.
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