Ponds for crab farming should be constructed in sunny, well-drained areas with flat slopes. The ideal size is between 3/15 to 1/3 hectare, ensuring a water depth of over 1 meter. A 30-50 cm high anti-escape structure should be built around the pond. To do this, dig a narrow ditch 30 cm deep around the pond, place stakes 50-70 cm above the ditch every 1-1.5 meters, and wrap the area with plastic film, securing it to the stakes. Fill the ditch with soil to bury the bottom edge of the film, preventing crabs from escaping.
Next, after clearing the pond, add fresh water and plant aquatic vegetation to provide shelter, food, and hiding places for the crabs. Plant species such as water hyacinth, duckweed, black grass, or even vegetables along the edges can be used. The coverage of aquatic plants should be at least one-third of the pond surface. Remove any leftover fish promptly to avoid contamination and water degradation.
Crab seedlings are typically stocked in May each year. During this time, it's crucial to prevent the appearance of premature (old) crabs, which can negatively affect growth. Stocking density should start at 400,000 per 1/15 hectare, and gradually adjust as the crabs grow. By the time they reach the IV larval stage, the density should be reduced to around 40,000 per 1/15 hectare.
Maintaining good water quality is essential. Water should be clean, with a transparency of over 40 cm, pH between 7.5 and 8.5, and dissolved oxygen levels above 4 mg/L. If water quality declines, flush the pond or use an aerator to improve conditions.
During summer, keep the water temperature between 18-23°C by using groundwater, cold springs, or reservoir water. Shade the pond area with grass during hot days to reduce heat stress on the crabs.
Feeding should follow the "two fine, middle green" principle. In spring and autumn, feed more concentrated animal-based food, while in summer, focus on green feed. Avoid overfeeding; allow crabs to eat until just full. Young crabs may stop feeding naturally, so ensure feed is fresh and not moldy.
Moss control is important, as it can harm aquatic plants and degrade water quality. Prevent moss growth by managing nutrients and, when necessary, using copper sulfate carefully. Avoid applying it during molting periods, and always change water after treatment. Manually remove moss when the pond is dry, and filter incoming water to prevent new moss from entering.
Disease prevention involves regular water disinfection. Apply lime every 10-15 days, using 20 kg per 1/15 hectare. This helps maintain water quality and sterilize the environment. Limit medication use and avoid drugs that could harm crabs. Always prioritize natural and safe management practices.
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