There are two main types of aquaculture—marine and freshwater. Moreover, the FAO also describes aquaculture as the captive rearing and production of fish and other aquatic animal and plant species under controlled conditions. Many aquatic species have been cultured, especially fish, crustaceans and mollusks and aquatic plants and algae. Aquaculture production methods have been developed in various regions of the planet, and have thus been adjusted to the distinct environmental and climatic conditions in different regions. The four major categories of aquaculture include open water systems (e.g.cages, longlines), pond culture, flow-through raceways, and recirculating aquaculture systems (RAS).

Fish eat the food and excrete waste, which is converted by beneficial bacteria to nutrients that the plants can use. In consuming these nutrients plants help to purify the water. Aquaponics integrates aquaculture and hydroponics into one production system. Aquaponics relies on the food introduced for fish, which works as the system’s input. As fish eat this food and process it, they transform it into urine and fecal matter, both rich in ammonia, which in sufficient quantities can be toxic to plants and fish. Afterward, the water (now ammonia-rich) flows, together with un-eaten food and decaying plant matter, from the fish tank into a biofilter. Afterward, inside this biofilter, bacteria break everything down into organic nutrient solutions (nitrogen-rich) for growing vegetables.

Reference- https://youmatter.world/en/definition/aquaponics-sustainable-benefits-system/