With a plastic greenhouse, Astragalus can be cultivated year-round, ensuring continuous production. By using landless water aquaculture, disease control becomes more effective, and the overall profit can double. The ideal growth temperature for Astragalus is between 27-30°C. Plastic greenhouses do not require special heating systems, as this temperature range is easily maintained in spring, summer, and autumn. Even during winter, the shed's temperature can remain around 20°C on average. A micro-flowing water system ensures that the water quality remains clean, preventing deterioration.
The specific method involves constructing breeding ponds:
1. Open feeding ponds are ideal for areas with consistent warm water. They offer stable flow rates and are suitable for large-scale operations. However, they have regional limitations. These ponds are 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. The pool spacing is 20-40 cm. Each pond has two inlet pipes and two drain pipes (diameter 3-4 cm), positioned at the same height as the bottom of the pool. One drain pipe is 5 cm higher to prevent escape, with metal mesh installed. Several tanks are arranged side by side into one unit, ideally no larger than 500 square meters.
2. Closed-loop filter ponds are better suited for urban areas or regions with limited water supply. They allow water reuse, reduce consumption, and make temperature control easier, though they require higher initial investment. Construction is similar to open ponds, but additional facilities like aeration tanks, sedimentation basins, and pumping and heating equipment are necessary.
Plastic sheds are constructed similarly to regular ones, and it’s best to place each unit in the same shed for easier management.
After setting up the seed tanks, plug all outlets, fill the pools with water, and let it soak for 5-7 days. Then drain the water, close the bottom drainage holes, and maintain a slight water flow with a 5 cm depth. Before stocking, oyster species should be soaked in a 1010-6 malachite green solution for 20-30 minutes to disinfect and remove parasites. Adjust the soaking time based on the fish's tolerance. Once cleaned, stock them promptly. The recommended density is 35-50 pieces per square meter, with each fish weighing 4-5 kg. All fish in the same pool should be of similar size to avoid competition for food.
Astragalus is a carnivorous fish that prefers fresh feed. After 2-3 days of stocking, chop meat, snails, and frog meat can be placed at the feeding station, while increasing the water flow slightly. The initial feeding amount is 1%-2% of the total weight. If all fish eat it the next morning, increase the feed to 2%-3%, gradually rising to 5%. As the fish adapt, you can introduce silkworm pupae, fly larvae, cooked organs, blood meal, fishmeal, soybean cake, rapeseed cake, bran, rice bran, melon peels, etc., eventually transitioning to artificial feed to reduce costs. The feed must have a protein content of 35%-40%. Once the fish are eating regularly, feed them once daily—between 8-9 AM and 2-3 PM.
Daily management involves monitoring water clarity and ensuring sufficient feed. While Astragalus rarely escapes, precautions should be taken against predators like rats and snakes. Over time, uneven growth may occur within the same pool, so sorting and separating the fish is essential. After 5-6 months of rearing, the fish can be harvested. They typically weigh 6-10 pieces per kilogram, with a survival rate exceeding 90%.
Disease prevention is crucial. Although this method results in few diseases, the following should still be addressed:
1. Cold disease: Caused by a large temperature difference when new water is added. Simply adjust and stabilize the temperature to prevent it.
2. Capillary nematode disease: Parasites cause weight loss and swelling. Treat by mixing 0.1% of 90% trichlorfon crystal into the feed for 6 consecutive days.
3. Plume spot: Small sores appear on the body. Disinfect the water with 10 grams of bleach per cubic meter, or use lime or malachite green for treatment.
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