Pangasius catfish (known locally as ikan patin) farming is one of Indonesia’s fastest-growing freshwater aquaculture sectors. According to the Ministry of Marine Affairs and Fisheries (KKP), production has surged in recent years – for example, rising from about 320,000 tons in 2017 to 391,151 tons in 2018 – as demand grows roughly 5–10% annually. Patin are prized for rapid growth, hardiness, and mild-tasting meat, making them popular with consumers at home and abroad (markets include Southeast Asia, the Middle East and Europe). Many farmers now favor the floating net cage (Keramba Jaring Apung, or KJA) system. In this method, square cages are installed in public waters (rivers, lakes or reservoirs), which cuts construction costs and labor. The flowing water naturally brings oxygen and keeps the fish clean, yielding a fresh, high-quality product. Indonesia’s abundant inland waters – home to 521 natural lakes (about 21,000 km² or ~8,000 sq mi in total) and thousands of kilometres of rivers – provide ample sites for KJA development. This means cage-based patin farming can be expanded to sustainably boost national production.

Construction of floating net cages

A typical floating net cage is a square frame roughly 4 meters (~13 feet) on a side. The frame sits on floats at the surface; the floor is open but lined with a fine mesh net that holds the fish. (The mesh size is chosen smaller than the juvenile fish so that they cannot escape.) In practice, cages are built in groups along the water’s edge. These clusters of cages are connected by simple bamboo or wooden walkways, allowing caretakers to easily move between them to feed the fish and inspect nets. The walkways’ ends are tied to poles driven into the lake or riverbed – this anchoring system keeps the cages from drifting or rocking under currents and waves. Above each cage cluster, a small stilted hut is often constructed. This caretaker hut serves as a lookout and storage shed for feed and equipment. Its presence provides shelter for staff and helps secure the farm, deterring theft or nocturnal predators.

he process of installing bamboo in a floating nate: Luhkan Kab Oki/Donna Octaviana

Site selection for KJA farming

Choosing the right site is crucial for KJA success. Farms need a reliable year-round supply of clean, well-oxygenated water. Research indicates that dissolved oxygen in the cage should be kept at least around 3 mg/L. If oxygen levels fall much below this (for example, under about 3–4 mg/L), fish growth can slow or stop, and there is risk of mass die-offs. Thus a strong water source (river or lake inlet) is essential. In addition, moderate water flow is beneficial: an ideal current speed is roughly 0.1–0.5 meters per second (about 0.2–1.1 miles/hour). This gentle flow continuously flushes out waste feed and excrement from the cages, preventing organic buildup and maintaining water quality. In practice, sites near horizontal flow channels or river mouths are often preferred. These areas tend to receive a steady inflow of fresh, oxygen-rich water and carry away waste, keeping conditions inside the cages clean and healthy.

Water quality criteria for pangasius farming in floating net cages

For pangasius to grow optimally in floating net cages, water quality must be carefully monitored and meet strict standards. Ideally, water temperature should remain between 20°C and 30°C (68–86°F) to ensure normal fish metabolism. The total dissolved solids (TDS) should not exceed 2,000 milligrams per liter, and water clarity should allow at least 45 centimeters (about 18 inches) of visibility. This level of clarity supports plankton photosynthesis, which provides a natural source of oxygen for the fish.

From a chemical perspective, stable water chemistry is also critical. The pH level should stay within about 6.0 to 9.0 to maintain a safe environment for the pangasius. Dissolved oxygen levels are equally important: at least 3 milligrams per liter of oxygen should be present for about eight hours each day. A sudden drop in oxygen can stress the fish, reduce their appetite, and greatly increase the risk of mortality.

Furthermore, concentrations of harmful compounds must be kept under strict control. Ammonia levels should not exceed about 0.016 milligrams per liter, and nitrite should remain below 0.2 milligrams per liter to avoid poisoning the fish. These water quality criteria must be maintained carefully, as even small fluctuations can seriously jeopardize pangasiushealth.

Potential challenges to floating-cage pangasius farming

Pangasius farming in open-water cages faces several challenges, many of them environmental. One common disturbance is the sudden upwelling of cold, deep water to the surface. This often happens at the start of the rainy season, when heavy rains cool the surface and cause denser bottom water to rise. That upwelling water can carry sediment and toxic compounds—such as hydrogen sulfide and ammonia—from the depths up to the cages. Researchers have found that even low concentrations of hydrogen sulfide (above 0.002 mg/L) can impair fish health and reduce survival rates, making this phenomenon potentially lethal for the stock.

Aside from natural events, water pollution poses a serious threat. Rivers and swamps in Indonesia are frequently contaminated by household waste, agricultural runoff, and industrial discharge. For example, decaying plant roots in wetlands and lakes release humic acids that can lower the water pH below 6.0. If not addressed, this increased acidity harms water quality and causes stress for the fish. In fact, data from the Indonesian Ministry of Environment indicate that roughly 75 percent of the country’s rivers are rated as lightly to moderately polluted, highlighting the severity of this problem.

Pangasius catfish vaccination activity: Luhkan Kab. Pasuruan/Aristya Rachmadani

Predators and pests are another recurring concern. The open location of floating cages leaves young pangasius vulnerable to animals like civets, monitor lizards, water snakes, turtles, herons, and even eagles. These predators may feed on the small fish, causing significant losses for the farm. Field reports suggest that without protective measures, predation can reduce the number of fry by 10 to 15 percent in a single production cycle. To combat this threat, farmers often set traps, install protective netting, and clear nearby vegetation that might conceal hungry predators.

Security is also an important consideration. Fish theft has been reported at some floating-cage sites. To prevent losses, operators implement strict security measures—especially at night—by stationing guards near the cages and installing locks on feeding ports. These precautions help safeguard the stock and protect the investment in each cage.