Cultivating astragalus in a plastic greenhouse allows for year-round production, making it an efficient and sustainable method. Soilless aquaculture not only helps control diseases but also significantly boosts profitability. The ideal growth temperature for astragalus is between 27°C and 30°C, which can be easily maintained in greenhouses without the need for additional heating systems. During spring, summer, and autumn, the temperature remains stable, while even in winter, the average temperature inside the greenhouse can reach around 20°C. Maintaining a steady flow of water in the rearing pond ensures good water quality and prevents deterioration.
First, constructing the breeding pond:
1. Open-flow ponds are suitable for areas with consistent warm water supply. They offer stable flow rates and are ideal for large-scale operations, though they are limited by location. These ponds are typically built using bricks and cement, with each pool covering 10–20 square meters, 40 cm deep, and 1–2 meters wide. The width of the pools is 20–40 cm. Each pool has two inlet and two outlet pipes (3–4 cm in diameter). The inlet pipe aligns with the bottom of the pool, while the outlet is slightly higher to prevent escape, with metal mesh installed. Multiple units can be arranged side by side, ideally no more than 500 square meters per unit.
2. Closed-loop filter ponds are better suited for urban areas or regions with limited water supply. They allow for water reuse, reduce consumption, and make temperature control easier, though they require higher initial investment. The construction is similar to open ponds, but they also include aeration tanks, sedimentation basins, and pumping and heating systems to maintain water quality.
Second, stocking the species:
After the pond is ready, drain all the water, refill, and let it soak for 5–7 days before draining again. Seal the bottom drain and keep a small amount of flowing water in each pool at a depth of 5 cm. Before stocking, the oyster species should be soaked in a 10â»â¶ malachite green solution for 20–30 minutes to disinfect and remove parasites. After sterilization, stock them at a rate of 4–5 kg per meter, ensuring that all individuals are of similar size to avoid cannibalism.
Third, feeding:
Astragalus is a carnivorous fish that prefers fresh food. After stocking, feed chopped snails, frogs, or other meat sources on a bait station, increasing water flow slightly. Initially, feed 1–2% of the total weight, and if all is consumed, increase to 2–3%, eventually reaching 5%. As the fish grow, introduce alternative feeds like fly larvae, cooked organ meats, fishmeal, soybean cake, and rice bran. Keep the protein content between 35–40%. Feed once in the morning and again in the afternoon when the fish are eating regularly.
Fourth, daily management:
With clear water and sufficient food, jaundice (a common term for astragalus) rarely escapes from the greenhouse. However, precautions must be taken against predators like rats and snakes. If the fish in a pool show uneven sizes, separate them promptly. After 5–6 months, they can be harvested, with a size of 6–10 pieces per kilogram and a survival rate exceeding 90%.
Fifth, disease prevention:
Although this cultivation method is relatively disease-free, some conditions may still occur.
1. Cold disease: Caused by sudden temperature changes during water exchange. Prevent it by gradually adjusting the water temperature.
2. Capillary nematode disease: Parasites cause weight loss, swelling, and death. Treat with 0.1% trichlorfon in feed for six consecutive days.
3. Plum spot disease: Causes red spots on the body. Disinfect the water with 10 grams of bleach per cubic meter, or use lime or malachite green for treatment.
By following these steps, you can ensure a healthy and productive astragalus farming operation.
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