Raising pangasius in earthen ponds has become a popular and promising aquaculture activity for many fish farmers. Known for its rapid growth and steady market demand, pangasius offers a profitable option for aquaculturists. While pangasius farming is relatively straightforward, achieving success requires careful preparation and well-thought-out planning. Each step—from selecting the soil type to pond design and water management—plays a critical role in determining the final yield. This article provides an in-depth look at the essential factors to consider when cultivating pangasius catfish in earthen ponds, aiming to minimize risks and optimize harvest results.
1. Soil type
Research indicates that sandy clay soils, such as gley and alluvial soils, are most suitable for pangasius farming. Gley soil, formed from deposits of alluvial materials in regions with annual rainfall over 1,500 mm, and alluvial soil, typically found in lowland floodplains, rivers, and lake basins, offer several advantages for fish farming. One of these advantages is their natural water-retention quality, which helps prevent leaks. Additionally, the dense texture of these soils makes it easier to construct embankments or pond walls, which are essential for keeping water contained.
However, not all land has ideal gley or alluvial soil. When the available soil is too loose, additional measures may be needed to make it suitable for fish ponds. For instance, loose soil often cannot retain water well, meaning pond walls may need an added layer, like cement or brick, to prevent leakage. While effective, this added layer can increase construction and maintenance costs.
A simple way to assess the suitability of soil for pangasius farming is to take a handful of moistened soil, squeeze it firmly, and observe the texture. If only a small amount of sand remains on the surface of your hand after squeezing, the soil can be classified as sandy clay, which has excellent water retention and is ideal for ponds. However, if a substantial amount of sand sticks to your hand, the soil is likely too loose. This type of soil, with larger pores, allows water to seep through, making it unsuitable for ponds without additional waterproofing layers.
2. Land contour
After analyzing the soil type, the next essential step in preparing a fish pond is assessing the land contour. Is the land flat or sloped? This aspect significantly affects the excavation methods and embankment construction required.
For sloped land, there is a natural advantage in managing water flow patterns. An ideal slope for fish ponds ranges between 3-5%, meaning a 3-5 meter height difference over a 100-meter pond length. This slope facilitates efficient water inflow and outflow, making water circulation management easier. Generally, with sloped land, excavation is required only on one side, with the dug-up soil then used to build embankments on the opposite side, saving both time and costs. This method enhances pond construction efficiency and optimizes soil resource use.
On flat land, excavation needs to be carried out on all sides of the pond to achieve the desired depth, and the excavated soil is then used to create embankments around the perimeter. Although flat-land excavation demands more effort and resources, this approach enables a more uniform and controlled pond shape. Additionally, flat terrain allows better control over water volume and quality since it isn’t affected by gravitational flow as it is on sloped land.
Excavation techniques for sloped and level ground
Whether on sloped or flat land, embankment construction requires careful attention. Embankments should be strong and watertight to prevent leaks. On sloped land, embankments built with excavated soil need to be well-compacted to prevent landslides. For flat land, embankments are typically built in a trapezoidal shape to increase stability and withstand water pressure.
Observing land contour also influences the placement of water inlets and outlets. On sloped land, it’s best to position the water inlet at the upper end of the slope and the outlet at the lower end, leveraging gravity for efficient water circulation. On flat land, the placement of inlets and outlets should be carefully designed using a piping or channel system that allows for effective water circulation.
3. Pond embankments
Embankments play a vital role in retaining water within a pond and protecting it from overflow during heavy rain or floods. A sturdy, waterproof embankment is essential to prevent leaks and ensure the stability of the pond. Selecting the right type of soil for embankment construction is crucial. Clay or sandy clay soils are ideal due to their sticky, non-porous nature, resistance to cracking, and strong water retention, making them excellent for building stable and long-lasting embankments.
The size of the embankment should match the pond's dimensions and planned water depth. A well-constructed embankment should extend at least 20 cm below the pond floor for additional stability, reducing the risk of landslides. Both sides of the embankment should be sloped to enhance stability, with the outer slope typically having a gradient of 1:1 to 1:1.5, while the inner slope is set at 1:1 for clay soil or 1:1.5 for less cohesive soil. This gradient helps distribute water pressure evenly, preventing structural damage to the embankment.
The width of the embankment top is also an important factor. To ensure sufficient strength against water pressure, the top width should be at least one meter. This width provides space for necessary materials and allows optimal compaction. The embankment height should be set according to the pond’s size and intended water depth; generally, the top should be higher than the planned water surface to prevent overflow in extreme weather.
For example, a pond covering 2,000 square meters requires an embankment height about 30 cm above the water level. For a larger pond of 4,000 square meters, this height should increase to about 50 cm. These differences account for the larger water volume in bigger ponds, necessitating taller embankments for safe containment.
A trapezoidal embankment shape is recommended, with a broader base for enhanced stability and support against water pressure. A wider base evenly distributes water pressure, reducing the risk of erosion or structural damage. This shape also allows for better compaction during construction, ensuring a more durable embankment.
• Symmetrical trapezoidal embankment
A symmetrical trapezoidal embankment with a 1:1 slope ratio provides reliable stability to contain the pond’s water.
Trapezoidal embankment with symmetrical sides
• Asymmetrical trapezoidal embankment
An asymmetrical trapezoidal embankment, with a 1:1.5 slope, is suitable for less cohesive soils, offering effective water retention adjusted for soil conditions.
Trapezoidal embankment with asymmetrical sides
4. Pond bottom
The bottom of a pangasius fish pond should ideally slope toward the drainage channel with a gradient of about 1-2%. This means there should be a height difference of 1-2 meters for every 100 meters of pond length, which aids in directing water flow toward the drain. This slope facilitates the removal of feed remnants and fish waste, promoting pond cleanliness and fish health. After shaping the pond, initial preparation includes draining and drying the pond bed until it is completely dry. This drying step is essential to break the life cycle of any pathogens present in the pond. Once the pond bed is dry, the soil should be tilled to a depth of about 10 cm to improve soil structure and aeration.
Following soil preparation, agricultural lime or dolomite is applied at a rate of about 2 tons per hectare to neutralize the soil pH, creating an optimal environment for pangasius growth. After liming, the pond bottom is fertilized with organic fertilizer, enriching soil fertility and providing essential nutrients for beneficial microorganisms in the pond ecosystem. The final preparation step is to fill the pond gradually with water. Gradual filling allows for temperature and water quality adjustments, ensuring even distribution throughout the pond to create an ideal habitat for the fish.
5. Pond inlet and outlet channels
Inlet and outlet channels are essential for maintaining effective water circulation in a pangasius pond. The inlet channel supplies fresh water continuously, preserving water quality to support fish growth. Conversely, the outlet channel removes wastewater containing waste and feed remnants, which, if accumulated, could degrade water quality. To ensure smooth circulation, the outlet channel should be larger than the inlet to increase wastewater removal capacity. Traditionally, inlet and outlet channels are made of bamboo or PVC pipes, which are affordable and readily available.
Maintenance of inlet and outlet water channels in ponds under varied conditions during the rainy season: BPBAT Tatelu
The inlet pipe is positioned at the top of the pond embankment, ensuring clean water enters without carrying debris from outside. The outlet pipe is located at the bottom of the pond, aligned with the pond bed slope, allowing wastewater to exit efficiently. Each water gate, both inlet and outlet, is fitted with a bamboo mesh filter to prevent debris or wild fish from entering the pond and to keep cultured fish from escaping.
6. Kemalir (fish channel)
A kemalir, or shallow trench, is an integral part of the pond, positioned either centrally or along the pond edges. It serves as a gathering place for fish when the pond water is lowered during harvest, making it easier to capture the fish. Additionally, the kemalir provides a refuge for fish from predators, drought, and direct sunlight. The size of the kemalir depends on pond size. For smaller ponds (100-500 square meters), a kemalir can be one meter wide and 30 cm deep. For larger ponds, it should be about 2-2.5 meters wide and 50 cm deep.
