With a plastic greenhouse, astragalus can be cultivated year-round, ensuring continuous production. By implementing landless water aquaculture, disease control becomes more effective, and overall profitability can double. The ideal growth temperature for astragalus is between 27-30°C, which is easily maintained in greenhouses during spring, summer, and autumn. Even in winter, the temperature inside the shed can average around 20°C without the need for additional heating. Maintaining a micro-flowing water system in the rearing pond ensures that water quality remains stable.
The construction of the breeding ponds involves two main methods: open feeding ponds and closed-loop filter ponds. Open feeding ponds are ideal for areas with consistent warm water sources, offering stable flow rates suitable for large-scale operations. However, they are regionally limited. These ponds are typically built using bricks and cement, with each pool covering 10-20 square meters, a depth of 40 cm, and a width of 1-2 meters. Inlet and outlet pipes, 3-4 cm in diameter, are installed at the same level as the pool bottom, with metal mesh to prevent escape. Multiple tanks are arranged side by side, ideally within a unit area of no more than 500 square meters.
Closed-loop filter ponds are better suited for urban areas or regions with limited water supply. They allow for water reuse, reduce consumption, and offer better temperature control, though they require a higher initial investment. The construction method is similar to open ponds, but additional components such as aeration tanks, sedimentation basins, and pumping systems must be included.
Plastic greenhouses are constructed like regular sheds, and it’s best to place each unit in the same structure for easier management. After setting up the seed tanks, the total water outlet should be sealed, and the pools filled with water for 5-7 days before draining. The drainage hole at the bottom should then be plugged, and water should be kept flowing at a depth of 5 cm. Before stocking, oyster species should be soaked in a 10 ppm malachite green solution for 20-30 minutes to disinfect and remove parasites. Stocking density is approximately 35-50 pieces per square meter, with fish size matching to avoid cannibalism.
Astragalus is a carnivorous fish that prefers fresh feed. After 2-3 days of stocking, chopped snails, frogs, and other proteins are placed on feeding stations, with increased water flow. Initially, feed should be 1%-2% of the total weight, increasing gradually to 5% as the fish adapt. Over time, artificial feeds such as silkworm pupae, fly larvae, cooked organs, fish meal, and plant-based meals can be introduced to reduce costs. The protein content of the feed should remain between 35%-40%. Feeding is done once daily in the morning (8-9 AM) and again in the afternoon (2-3 PM).
Daily management in plastic greenhouses is straightforward due to clear water and sufficient food supply. Astragalus rarely escapes, but precautions must be taken against predators like rats and snakes. If uneven growth occurs in the same pool, fish should be separated promptly. After 5-6 months of rearing, they reach market size—6-10 pieces per kilogram—with a survival rate exceeding 90%.
Disease prevention is minimal with this method, but some common issues still require attention:
1. **Cold Disease**: Caused by sudden temperature changes when new water is added. Adjusting and stabilizing the water temperature prevents this.
2. **Capillary Nematode Disease**: Parasites cause weight loss, swelling, and death. Treat with 0.1% trichlorfon crystal mixed into feed for six consecutive days.
3. **Pimple Spot Disease**: Characterized by small sores on the body. Disinfect the water with 10 grams of bleach per cubic meter, or use lime or malachite green.
By following these practices, farmers can ensure healthy, high-yield astragalus cultivation with minimal risk.
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