Pond Aquaculture: A Guide to Earthen Pond Fish Farming

How earthen-pond fish farming works: construction, fertilization and liming, stocking, polyculture, water-quality and oxygen management, and harvesting.

Overview

Pond aquaculture is the rearing of fish in constructed earthen ponds, and according to FAO it is by far the most widespread culture method in inland aquaculture worldwide. Inland aquaculture produced about 54.4 million tonnes in 2020, around 44 percent of total aquaculture output of aquatic animals and algae. Ponds either rely on natural food, supplemental feed, or both, depending on the intensity of the operation.

Pond construction and water supply

FAO production manuals describe a minimum depth of about 80 cm at the shallow end, with pond width generally not exceeding 100 m and individual pond size kept to roughly 5–10 ha so that filling, draining and harvesting remain practical. Ponds require a reliable water supply to offset losses; in tropical climates evaporation can reach several millimetres per day, and continuous inflow may be needed to maintain level. Source water is assessed for suitability before stocking.

Culture intensity

• Extensive: relies on natural food produced in the pond, with no formulated feed.
• Semi-intensive: natural food supplemented with fertilization and partial feeding.
• Intensive: complete formulated feed and aeration to maximize yield per hectare.

Fertilization and natural productivity

Fertilizers raise the production of natural food organisms—phytoplankton, zooplankton and insects—creating a plankton bloom that colours the water green. FAO notes that phosphorus is the nutrient most often limiting in natural waters. Inorganic fertilization for one production cycle is on the order of 30–60 kg P2O5, 40–100 kg N and 35–80 kg K2O per hectare. Organic manures are also used, with safe maximum loading of roughly 60 kg dry matter per hectare per day in temperate climates and up to about 120 kg in the tropics. The Secchi disc guides dosing: transparency below about 25 cm signals no fertilization is needed, while 40–60 cm indicates routine application.

Liming

Liming raises alkalinity and buffers pH toward neutral or slightly alkaline, improving the response to fertilization and overall production. FAO guidance advises separating liming and manuring by at least about 15 days to avoid chemical reactions that reduce fertilizer effectiveness. Reported trials show measurable yield increases when ponds with low alkalinity are limed.

Stocking, polyculture and species

Common pond species include carps (Cyprinus carpio and the Chinese carps), tilapias (Oreochromis niloticus, O. mossambicus) and catfishes. Polyculture combines species that occupy different feeding niches—for example bottom-feeding carp, plankton-filtering silver carp, herbivorous grass carp and detritus-feeding mullet—to use the pond more fully. FAO describes representative polyculture stocking of roughly 3,000–6,000 carp, 3,000–4,000 tilapia, 500–1,500 silver carp, about 1,000 mullet and about 300 grass carp per hectare, for total densities near 7,000–9,500 fish per hectare. Tilapias breed early, so monosex culture or predator stocking is often used to control reproduction.

Supplemental feeding

As the standing crop rises, natural food becomes insufficient and formulated feed is added. FAO feeding guides shift the ration from cereals such as sorghum at low standing crops toward higher proportions of protein pellets (around 25 percent crude protein) as biomass increases, until pellets supply the entire ration at high standing crops. Feed is distributed at fixed points and amounts are adjusted to temperature so that feed is consumed before the next distribution.

Water quality and dissolved oxygen

Dissolved oxygen is the most critical parameter. FAO manuals list desirable DO around 7–10 ppm with about 5 mg/L as a practical minimum, pH near 6.9–9.0, and low ammonia. As stocking and feeding intensify, oxygen demand rises. Symptoms of depletion include fish gasping at the surface, stopping feeding, and erratic movement. Aeration is used at high densities; FAO indicates it becomes obligatory for much of the night and early morning at densities around 15,000–20,000 fish per hectare.

Harvesting

Ponds are harvested by netting and, for full harvest, by draining. FAO notes that pond size is chosen partly so a pond can be harvested by a working team within a reasonable time. After harvest the pond is dried, disinfected with lime, refilled and fertilized before the next stocking.