The farming of pangasius catfish (Pangasius sp.) is an increasingly attractive venture for aquaculture entrepreneurs, driven by its high economic value, relatively straightforward rearing process, and consistently growing market demand. While many fish farmers have traditionally cultivated pangasius in earthen or tarpaulin-lined ponds, a more permanent and durable alternative has emerged: concrete-walled ponds.
This method, while requiring a greater initial investment compared to its earthen or tarpaulin counterparts, offers commensurate returns in longevity and simplified management. Concrete ponds represent a strategic choice for experienced pangasius farmers ready to elevate their operations to a more serious, sustainable scale.
Site preparation
The initial step of preparing the land is critical to the success of cultivating pangasius in concrete ponds. Several factors must be carefully considered when selecting a site to ensure the cultivation process runs smoothly and efficiently. The chosen land should be flat or have a gentle slope to facilitate the construction of the pond. It is also advisable to select a site with sufficient area to accommodate all aquaculture activities, from hatchery and grow-out phases to harvesting, within a single location.
Furthermore, it is imperative to ensure the location is not susceptible to flooding and is distant from sources of water pollution, including both organic and inorganic waste. Proximity to agricultural areas such as rice paddies or plantations should be avoided due to the risk of pesticide contamination, which can severely compromise the water quality of the pond. An ideal site would also be situated at a lower elevation than its water source, allowing the pond to be filled using gravity, thereby reducing the operational costs associated with water pumps.
Finally, accessibility to the cultivation site is a crucial consideration. A location that is easily reached will simplify the logistics of distributing fingerlings and feed, as well as the transportation and marketing of the harvested pangasius catfish.
Types of concrete ponds and their characteristics
For the purpose of pangasius cultivation, concrete ponds are generally categorized into two primary types: in-ground and surface-level ponds. The selection between these two depends on the land conditions, the availability of a water source, and the construction budget.
1. In-ground concrete ponds
In-ground ponds are constructed by excavating the earth to a specific depth. This type is typically built near a natural water source, such as a river, that lies at a lower elevation than the surrounding ground. A key advantage of this design is the ability to fill the pond naturally, which can be a significant energy saver as it negates the need for mechanical water pumps.
In-ground concrete ponds: Luhkan Kab. Gunung Mas/Yunina
2. Surface-level concrete ponds
Surface-level ponds are better suited for hard or rocky terrain where excavation would be costly and time-consuming. The water for these ponds is usually sourced from dug wells, boreholes, or artesian wells. The use of municipal tap water is generally discouraged, particularly in urban areas, due to the high concentration of chemicals used for water treatment. If no other option is available, the tap water must undergo a neutralization process before being introduced into the pond.
It is essential to remember that the construction of these concrete ponds is a permanent investment. Therefore, the design and structural calculations must be meticulously planned to align with the initial capital outlay and the anticipated returns.
Optimal pond depth and stocking density
The depth of the concrete pond is a key factor that directly influences the growth of the pangasius catfish. For a standard five-month rearing cycle, an ideal depth ranges from 1 to 1.5 meters (approximately 3.3 to 4.9 feet). Ponds that are too shallow can cause undue stress to the fish due to limited space and rapid fluctuations in water temperature.
A frequently overlooked yet important step in managing concrete ponds is the installation of netting or a screen over the top. This serves the dual purpose of preventing the fish from leaping out and keeping external debris, such as dry leaves, from contaminating the pond water.
Regarding stocking density, data from the Buleleng Regency's Department of Food Security and Fisheries (DKPP) suggests an ideal rate of 20 to 30 fish per cubic meter of water. To illustrate, a concrete pond measuring 10 by 10 meters with a depth of 1 meter holds a water volume of 100 cubic meters. Such a pond can comfortably accommodate between 2,000 and 3,000 pangasius fingerlings. Exceeding this ideal capacity will not necessarily increase the final yield; on the contrary, it poses a significant risk of mass mortality resulting from oxygen depletion and competition for feed.
The importance of an effective water circulation system
Pangasius catfish thrive in clean, clear water, free from sediment, which is essential for their optimal growth. Poor water quality can lead to a decrease in dissolved oxygen levels, induce stress, and facilitate the spread of diseases that can be detrimental to the entire fish population. Research indicates that the ideal dissolved oxygen concentration for pangasius cultivation is between 3 to 5 mg/L, with an optimal water temperature ranging from 26°C to 30°C (79°F to 86°F) and a pH level between 6.5 and 8. Consequently, managing water circulation is a critical factor that cannot be overlooked in this aquaculture practice.
In the design of concrete ponds, the drainage system must be carefully engineered. At a minimum, the pond requires two types of outlets: one for draining dirty water and sediment that settles at the bottom, and an emergency channel to discharge excess water during heavy rainfall to prevent flooding. A well-functioning circulation system also helps maintain stable water temperatures, especially during prolonged dry seasons.
The process of filling a concrete pond should be done gradually to avoid stressing the pangasius fingerlings. Initially, the pond should be filled to a depth of only 30 to 40 centimeters (about 12 to 16 inches), allowing the young fish to easily reach the surface for oxygen. After two weeks, the water level can be increased periodically by about 10 centimeters (4 inches) each week until the ideal depth of 100 to 150 centimeters (3.3 to 4.9 feet) is reached. This phased-filling technique has been shown to reduce fingerling mortality by up to 20 percent compared to filling the pond completely from the start.
Techniques for stocking pangasius fingerlings in concrete ponds
Before introducing the fingerlings, it is crucial to calculate the appropriate stocking density for the pond's volume. The stocking itself should be performed using an acclimatization method. This involves floating the sealed plastic bags containing the fingerlings on the pond's surface for 10 to 15 minutes. This allows the temperature of the water inside the bag to gradually match the temperature of the pond water.
Once the temperatures have equalized, the bags should be opened slowly, permitting the fingerlings to swim out on their own. This simple yet effective procedure helps prevent shock and stress in the young fish that can result from abrupt changes in temperature and water chemistry.
Pest and disease control in concrete pond cultivation
Pests such as water snakes, predatory birds, monitor lizards, water civets, and even turtles often pose a serious threat to Pangasius farming in concrete ponds. The presence of these predators not only results in the direct loss of fish but can also cause significant stress among the remaining stock, leading to a decreased appetite and inhibited growth. To counter these threats, farmers typically employ several preventative measures, including installing protective netting over the ponds, erecting security fencing around the cultivation area, and conducting routine inspections of the ponds, particularly in the morning and evening.
Beyond pests, disease presents another major challenge. Contagious diseases, including bacterial, fungal, and parasitic infections, can spread rapidly, especially in ponds with poor water quality. Meanwhile, non-contagious ailments are often caused by environmental stressors, oxygen deficiency, or improper feed management.
Harvesting techniques in concrete ponds
The harvesting of pangasius catfish from concrete ponds is generally timed according to market demand and the farm's management strategy. A method known as partial harvesting is often employed by farmers who wish to maintain a continuous supply. In practice, this involves lowering the pond's water level to a certain point to make the fish easier to catch. The fish are then sorted by size, with those meeting the desired market weight—for instance, 800 grams to 1 kilogram (1.8 to 2.2 pounds) per fish—being harvested. Fish that are still too small are returned to the pond to continue growing, ensuring a year-round harvest potential.
Pangasius fish ready for harvest after reducing the water level in the pond: Luhkan Kab. Gunung Mas/Yunina
Alternatively, a total harvest is typically conducted when a farmer intends to start a new cultivation cycle or when market prices are particularly favorable. This process involves completely draining the pond to collect all the fish at once. This method is considered more practical for population control and sanitation, as it provides an opportunity to thoroughly clean the pond, make any necessary repairs, and prepare it for the next batch of fingerlings.
