Detailed Explanation of Key Techniques for Loach Farming on Rooftops

Loach Pond Construction

The rooftop where the loach pond is built should have reinforced steel-concrete floor slabs, with waterproofing treatment applied on top. The pond walls follow the pattern of "24-brick outer walls and 12-brick inner walls," with a height of 0.7 m to 1.0 m. During construction, the sand-mortar ratio should be above 1:2.5, and 8 mm iron wire should be added as reinforcement every 4 to 6 bricks in thickness. Vertical iron wires are set at the four corners of the rooftop in 2 to 3 runs, forming a warp-and-weft distribution with horizontal iron wires. The size of the loach pond depends on the rooftop area. The four corners are rounded off, and drainage channels and insertion holes for protective shading support rods are reserved in advance. The loach pond should align with the building's foundation to avoid displacement that could reduce the safety coefficient. The supporting facilities of the loach pond include three aspects:

1. Water inlet and drainage system: Since underground well water and tap water that have not been exposed to sunlight are not suitable for direct use, a storage tank or large iron box with a drop and a height of 1.5 m to 2 m should be set up beside the main-house loach pond, so that the water source can mix and buffer before flowing into the loach pond by gravity. The main-house pond serves as the fry and first-stage grow-out pond, while the side-house pond serves as the second-stage grow-out pond. Since the main house is higher than the side house, water from the first-stage pond flows by gravity into the second-stage pond, and after multiple uses is discharged into the pig pen or an outdoor water channel.

2. Protective netting: Set up protective netting 40 cm to 50 cm above the pond surface to prevent direct sunlight and damage from rats and birds.

3. Simple temperature shed: Given that the suitable growth temperature for loach is 20°C to 30°C, in low-temperature seasons, build an easily disassembled or roll-up simple temperature shed to keep the temperature inside above 20°C, ensuring normal growth of the loach and shortening its market cycle.

Fry Release and Grow-Out

1. Fry sources

There are two channels for fry sources: one is collecting wild natural fry. In shallow waters such as wild ponds and ditches where loach prefer to inhabit with deeper bottom mud and rich humus, choose evening time to capture wild fry using bamboo cages baited with roasted soybean cake, animal offal, and the like. The captured wild fry should be screened to remove the weak and keep the strong before use. The second is semi-artificial breeding. During the breeding season, from the captured wild brood fish, select individuals with a female-to-male ratio of 1:2 to 3, with upright body shape, normal color, free of disease and injury, fully 2 years old, and weighing over 30 g, keep them temporarily for several days, then place them in a spawning pond to spawn naturally. The spawning pond should first be disinfected, then spread with 15 cm to 20 cm of fertile mud, fertilized with organic fertilizer to enrich the water, and the water temperature controlled above 18°C. For the obtained egg masses, bundle them with willow roots, palm fiber, polyethylene fiber threads, etc., disinfect them, and hang them evenly in the pond water. After spawning, move the egg masses into a hatching pond for incubation, obtaining fry in batches by stages. During incubation, maintain still water or slight aeration. After the fry hatch out of the membrane, promptly remove the egg masses and begin feeding and cultivation. Suitable feeds include egg yolk, fish meal, small algae, rotifers, silkworm pupa powder, soybean milk, etc. When the fry grow to 1 cm, divide them into separate ponds; when they reach 3 cm, put them into large ponds for grow-out.

2. Fry stocking

The stocking time depends on the source of the fry. For wild fry, it is from late April to mid-May; for semi-artificial fry, 15 to 30 days earlier. Stocking density is 2000 to 4000 fish per sq m for those within 1 cm in body length; 300 to 500 fish per sq m for those within 3 cm; and 50 to 85 fish per sq m for those over 3 cm. Before stocking, disinfect old ponds with disinfectant; for new ponds, soak first and then disinfect. Spread 20 cm to 40 cm of fertile mud or fine sand on the pond bottom, fill with water to 30 cm to 50 cm, and apply sufficient base fertilizer to breed basic biological feed. Keep the pond water transparency between 15 cm and 25 cm. At this point, screen and disinfect the loach fry, and stock them into the ponds for grow-out according to the stocking requirements for different sizes.

3. Feeding management

Loach are omnivorous and have no strict requirements for food. In the early stage of farming, focus on fertilizing the water quality and breeding plankton feed, supplemented with an appropriate amount of egg yolk, earthworms, silkworm pupae, soybean milk, etc. Different feeds should be slightly processed according to the degree of mouth opening of the loach fry, and the daily feeding amount should be controlled at 2% to 5% of the fish body weight. In the middle and later stages of farming, mainly feed artificial feeds such as rice bran, fish meal, livestock and poultry offal, wheat bran, and soybean residue. During this period, as the water temperature rises, the loach enter their peak growth period, and the daily feeding amount needs to be increased to 5% to 10% of the fish body weight. Because the loach pond is built on the rooftop, exposed above and with a house below, the pond water temperature varies greatly, and sudden cold and heat can easily cause management to get out of control, leading to imbalanced growth of the loach. Therefore, in the early stage of farming and during overwintering management, supplement with a simple temperature shed; when cold waves bring temperature drops, use soil heating or coal stoves for artificial temperature control. In the middle stage of farming during the peak summer season, build shading sheds, increase the frequency of water changes, and keep the water temperature relatively stable. Pay attention to preventing snakes, rats, and birds to avoid damage.

4. Disease prevention and treatment

Common diseases include red-fin disease, saprolegniasis, gas bubble disease, and parasitic diseases, among others. Their causes and treatment methods are as follows: red-fin disease is mostly caused by fish body injury, water deterioration, and bacterial infection, and is highly harmful to loach with a relatively high incidence rate. Soak in 10 ppm tetracycline for 24 hours or splash diseased fish with 1 ppm available chlorine; for severe cases, add 1% to 2% antibiotic medicated feed, and the curative effect is quite good.

Saprolegniasis

Caused by relatively low water temperature and fish body injury. Soak the diseased fish in salt water for 5 to 10 minutes. Gas bubble disease is caused by excessive gas in the pond water; pay attention to feeding an appropriate amount and preventing water quality deterioration or over-fertilization, and it can be cured. For parasitic diseases, splash the entire pond with 0.7 ppm of a mixture of copper sulfate and ferrous sulfate at a ratio of 5:2.