The earliest example of aquaculture can be found in South China, Thailand, and Indonesia, where the cultivation and farmimg rice in paddy fields in combination with fish are cited as examples of early aquaponics systems. The ancient Chinese employed a system of integrated aquaculture in which finfish, catfish, ducks and plants co-existed in a symbiotic relationship. The ducks were housed in cages over the finfish ponds, and the finfish processed the wastes from the ducks. In a lower pond, the catfish live on the wastes that have flowed from the finfish pond. At the bottom of the system, the water from the catfish ponds was used for irrigated rice and vegetable crops.
As many edible aquatic and semi-aquatic organisms have always been part of these ecosystems, the capture of wild fish, frogs, shrimps, clams, and snails in rice fields and irrigation channels has been a common practice in most Asian countries. Rice paddies have lots of natural food for fish. This is one of the advantages of raising fish and rice together. Fish help the farmer by eating weeds and insects in the paddy field. And they fertilize the rice with their manure. On top of all this fish is a nutritious food for your family. Raising young fish in the paddy fields before spring transplanting is an effective way to resolve the problem of getting a source of young fish for ponds and reservoirs in the mountainous regions.
When fish were introduced into flooded paddy fields, farmers were able to grow the same amount of grain as in conventional rice monocultures. The fish reared can be of carp species which is considered a delicacy, so farmers could sell them. They could also make large savings on fertilisers and pesticides, which typically represent 60–70 per cent of the total cost of rice production. Fish significantly lower the risk of rice sheath blast disease and reduce the amount of weeds and harmful pests such as the rice planthopper.
In reality, aquatic or terrestrial weeds also grow in rice fields along with phytoplankton and photosynthetic bacteria. They absorb the nutriments in the field. While these biomass are of no use to mankind, they are competitors for the nutriments with paddy. However, all of them are excellent food organism of fish. If fish are cultured in the fields, almost all the biomass could be utilized by fish resulting in effective utilization of the nutrients in the fields. The excreta of fish directly fertilise the water in rice fields. It has been seen that the concentration of nitrogen, phosphorus and potassium in rice fields with fish culture is higher than those without fish culture.
Paddy field where water stays for a certain time in special depth is undoubtedly an ideal environment for fish. Generally, seasonal rain water is the main water source of paddy field. The fish feed which grows naturally by amalgamation of fertilizer, dung, water and soil of paddy field is very suitable for fish production. So, a farmer can earn some extra income by farming fish in the paddy field. Stocking little amount of tilapia, common carp etc. in paddy field is very profitable. Those fishes are very fast growing, tasty and has a high value in the market.