Snail-shrimp-grass green three-dimensional planting and breeding and blue-green algae prevention and control method

Abstract

The invention discloses a snail-shrimp-grass green three-dimensional planting and breeding and blue-green algae prevention and control method. The planting and breeding system is constructed through layered utilization of water resources. Chubs are stocked on the upper layer, crayfishes are bred on the middle-lower layer, bellamya is put on the bottom layer, and an underwater three-dimensional space is constructed in cooperation with waterweed and high-temperature-resistant vallisneria nana. According to the method, specific fry specifications, bait formulas and feeding management are adopted, the three-dimensional oxygenation technology is combined, the yield per mu of snails is 800-1000 jin, the yield per mu of crayfishes is 200 jin, more than 60 jin of egg-carrying crayfishes are obtained in batches per mu, and compared with a traditional mode, the benefit is increased by 150%. Meanwhile, by means of the synergistic effect of the vallisneria nana, the bellamya and the chub, growth of the blue-green algae is inhibited, the blue-green algae outbreak risk is reduced by 60-70%, and peripheral ponds can be connected in series to purify tail water for cyclic utilization. The mode gives consideration to economic benefits and ecological benefits, reduces the breeding cost, and realizes peak-shifting high-price marketing of the crayfishes.

Description

Technical Field

[0001] This invention belongs to the field of aquaculture and relates to a green three-dimensional farming method for snail-shrimp-grass and a method for controlling cyanobacteria. Background Technology

[0002] In the current development of aquaculture and related industries, multiple demands and pain points are intertwined. From the perspective of industry demand, the snail market presents a significant supply-demand imbalance. On the one hand, snail supply is highly dependent on natural resources, but with the depletion of natural resources and strengthened resource protection, coupled with the popularity of trendy restaurants like "snail rice noodles" and the demand for fresh bait and environmental purification in the main crab producing areas of the middle and lower reaches of the Yangtze River, demand is growing rapidly, leading to a severe shortage of snails. Market demand is forcing the development of the snail farming industry. On the other hand, wild snails pose quality and safety risks—freshwater snails mostly inhabit bottom mud, accumulating environmental pollutants, while most edible snails come from wild water bodies with unclear environmental backgrounds; at the same time, large-scale snail farming has high technical barriers, and the *Bellamya aeruginosa* has stringent requirements for the bottom environment. Improper farming management can easily lead to large-scale mortality and may also pollute water quality and cause the death of other farmed organisms. The economic output of monoculture snail farming also has obvious shortcomings. Currently, large-scale snail farming in China is still in its infancy. Supply mainly relies on wild harvesting and polyculture in fishponds (primarily fish, with snails as a byproduct). Yields are typically 300-500 jin (150-250 catties), with a price of about 2 yuan / jin (0.5 yuan / catties), resulting in an economic output of less than 1,000 yuan per unit area. Furthermore, large-scale farming technology has not yet been mastered, and high density leads to increased mortality rates. The high cost of wastewater purification and blue-green algae control in conventional farming is also a major pain point for the industry. Meanwhile, crayfish farming is mainly based on rice-crayfish integrated farming. Due to the rice planting cycle, crayfish are mostly harvested before the end of June, resulting in a short growth period and smaller size (especially in Jiangsu and Anhui provinces). During the high-temperature season, crayfish are easily forced into burrows, reducing market supply. High-quality, large-sized crayfish and berried crayfish suitable for breeding are particularly scarce, keeping prices high. These industry pain points collectively constitute a real need for technological innovation.

[0003] From the current situation both domestically and internationally, existing technologies have many shortcomings. Regarding snail farming, related research is mostly limited to biological characteristics and water purification; large-scale pond farming is rare, and supply relies on wild harvesting or polyculture in fishponds, resulting in low yields per acre, with large-sized snails accounting for only 10%-20%. Crayfish farming, due to its limited production model, experiences concentrated market entry, leading to large price fluctuations and supply shortages after July. In terms of aquatic plant cultivation, existing aquatic plants (such as *Elodea nuttallii*) are not tolerant of high temperatures and easily rot and die in summer, damaging water quality. Regarding cyanobacteria control, current technologies focus on natural water body restoration, but the high-temperature decay of *Elodea nuttallii* in aquaculture ponds easily triggers cyanobacteria blooms, resulting in high treatment costs. Summary of the Invention

[0004] The purpose of this invention is to address the aforementioned shortcomings of the prior art by providing a green, three-dimensional farming method for snail-shrimp-grass and cyanobacteria control.

[0005] The objective of this invention can be achieved through the following technical solutions:

[0006] A three-dimensional aquaculture method integrating snails, shrimp, and aquatic plants includes: raising silver carp in the upper and middle layers of the pond, stocking 80-150 fry per mu (approximately 0.067 hectares); raising crayfish in the lower and middle layers of the pond, stocking 2000-5000 fry per mu in early April; planting Elodea nuttallii from December of the previous year to February of the following year, and planting Vallisneria natans in February and March to construct an underwater three-dimensional spatial framework; and raising Bellamy chinensis in the bottom water of the pond, stocking 300-500 jin (approximately 150-250 catties) per mu from December to March of the following year. The Bellamy chinensis feeds on uneaten food, feces, and other organic debris and attached algae, while also attaching and climbing among the underwater forest of Vallisneria natans. This invention constructs a three-dimensional aquaculture system that, vertically, purifies the water by creating an upward three-dimensional space through aquatic plants; horizontally, it creates spatial divisions for Vallisneria natans cultivation and crayfish growth through pond enclosure netting, all of which are beneficial to the growth of aquatic plants, crayfish, and snails during hot weather. Bottom-cultured *Bellamya aegyptiaca* feeds on uneaten food, feces, and other organic debris, as well as attached algae. It can also attach and climb on the underwater forest of *Vallisneria natans*, whose broad, flat leaves are suitable for snail climbing and algae attachment. This invention creates a year-round aquatic plant environment for crayfish, increasing their space for activity within the mid-layer aquatic plants. This helps crayfish avoid predators and cannibalism (especially in hot weather, the plant cover helps lower the water temperature, which is beneficial for crayfish growth), improving quality, yield, and size. The resulting crayfish have a high spawning rate and high-quality eggs in September and October, making them suitable for use as broodstock. This three-dimensional system maximizes the utilization of organic residues in the water and provides maximum attachment and growth space for *Bellamya aegyptiaca*. (Another important function is that, given that cyanobacteria are a major challenge in aquaculture during hot weather, this combined animal and plant biological regulation method helps control and inhibit cyanobacteria growth.) By utilizing water resources in a stratified manner (upper layer silver carp, middle layer shrimp and grass, bottom layer snails and shrimp), spatial complementarity is achieved, with a yield of 800-1000 catties of snails and 200 catties of crayfish per mu, which is 150% higher than the traditional model.

[0007] As a preferred embodiment of the present invention, the silver carp fry are 2-4 cm in size per fish. Practice has shown that fry of this size have the best effect in controlling blue-green algae and have less competition for aquatic food, while filter feeding on phytoplankton.

[0008] As a preferred embodiment of the present invention, the size of the crayfish seedlings is 80-120 crayfish / jin (approximately 500 grams).

[0009] As a preferred embodiment of the present invention, 400-500 catties of ringed snails are released per mu, of which 300-400 snails per catty weigh 300-350 catties.

[0010] As a further preferred embodiment of the present invention, the feed formula for the ringed snail is freshly cooked indica rice and soybean residue mixed evenly at a weight ratio of 3:1, and fed immediately after preparation.

[0011] As a further preferred embodiment of the present invention, from April to June and from September to November, the feed is evenly scattered along the edge of the pond at a depth of 40cm below the surface every evening from 5 pm to 6 pm. If there is still feed left the next morning, the amount of feed for that day should be appropriately reduced so that it can be seen by the naked eye that the snails have finished eating by the next morning. In other months, the snails can be fed 2-3 times a week depending on their activity, with the goal of finishing the feed within 2-3 days.

[0012] As a preferred embodiment of this invention, *Vallisneria natans* (different from conventional *Vallisneria natans*, this aquatic plant does not emerge from the water surface and exhibits better high-temperature growth performance) and *Elodea nuttallii* are planted in sections within the pond: 50%-60% of the pond's central area is enclosed by a net for planting *Vallisneria natans*, while *Elodea nuttallii* is planted outside the netting. The combination of *Vallisneria natans* and *Elodea nuttallii* is primarily based on temporal and spatial considerations. *Elodea nuttallii* is a cold-water aquatic plant, suitable for growth in the middle and lower reaches of the Yangtze River from January to May, gradually dying off after the high temperatures in June; while *Vallisneria natans* is a heat-tolerant aquatic plant, showing excellent growth advantages during the high-temperature season from June to August. The aquatic plants in high-temperature conditions play a crucial role in the success or failure of the entire aquaculture process. Planting *Vallisneria natans* and *Elodea nuttallii* in sections within the pond avoids early cover-up of *Vallisneria natans* by *Elodea nuttallii*, which would inhibit its growth. The method of this invention ensures that ponds using this method are covered with 50-60% dwarf Vallisneria natans during hot summer days, along with some Elodea nuttallii. This greatly reduces the incidence of aquatic plant decay and death during hot summer days in traditional farming methods, providing shade for crayfish during hot weather, thus guaranteeing the growth of farmed crayfish and snails and significantly improving their quality.

[0013] As a preferred embodiment of the present invention, Elodea is used as a transitional aquatic plant in the pond from February to April. The growth of Elodea is strictly controlled in April and May. Before the high temperature in July, the tops of the plants that have grown above the water surface are cut every two weeks to leave 30-40 cm above the mud, clearing the waterways and leaving space in the water for Elodea to grow. After June, if Elodea is found to be decaying or dying, it should be removed in time to prevent water quality from deteriorating.

[0014] As a preferred embodiment of the present invention, the pond adopts a three-dimensional aeration method of "bottom micropore aeration + surface waterwheel aeration". Generally, the micropore aeration is turned on at night, and the waterwheel is turned on for 2-3 hours at noon during the day to maintain the dissolved oxygen at 3.5-4.5 mg / L at night and 5 mg / L during the day.

[0015] As a preferred embodiment of the present invention, a pipeline is connected in series with surrounding crab ponds and crayfish ponds. If blue-green algae blooms occur at a nearby pond, its effluent can be directly discharged into the pond described in claim 1 to suppress blue-green algae and purify and recycle it.

[0016] Beneficial effects:

[0017] This patented technology constructs a multi-species synergistic system with snails as the main component, exhibiting strong ecological stability and producing marketable snails, crayfish, and Vallisneria natans. Simultaneously, the crayfish can be sold at higher prices during off-peak seasons, achieving economic benefits from multiple varieties. In addition to its aquaculture functions, the system also purifies pond wastewater, inhibits cyanobacteria, and promotes recycling. It is particularly effective in controlling and suppressing cyanobacteria blooms that are prone to occur in aquaculture ponds during the summer, significantly reducing the substantial economic costs of algae control and the risks associated with pest control. The *Bellamya aquatica* raised using this method are large, high-quality, and have a clear body surface. From March to Qingming Festival, the yield is 800-1000 jin (400-500 catties) of high-quality snails per mu (0.067 hectares), with a size of 100-150 snails per jin, and a market price of 8 yuan per jin. From July to September, 100-150 jin (500-650 catties) of high-quality crayfish can be harvested. These crayfish are plump, with over 70% weighing more than 35g per crayfish. They have high gonad fullness and can be used as broodstock or sold as finished products, with a market price of 60-80 yuan per jin. Large-sized crayfish are scarce from July to September, resulting in higher prices. The crayfish have a high spawning rate in October, leading to significant economic benefits. This method reduces feed consumption in ponds by about 10-15% compared to conventional methods. The low-growing *Vallisneria natans*, leftover feed, and self-produced juvenile snails in the pond complement the crayfish's diet, resulting in high feed utilization and less sediment in the pond.

[0018] Bellamya can consume cyanobacteria to a certain extent (daily intake of 5% of body weight), and silver carp filter-feed on algal spores, thus inhibiting cyanobacteria blooms in ponds. By connecting with surrounding crab and crayfish ponds, it partially purifies the ponds. During the high-temperature season, if cyanobacteria blooms occur in a pond, its wastewater can be directly discharged into the pond designed using this invention. This invention is the first to propose a synergistic algae control technology combining *Vallisneria natans* and Bellamya, utilizing a constructed "snail-grass" system to purify and eliminate cyanobacteria. Simultaneously, the purified pond water is recycled. Since the snails consume 3-5% of their body weight in cyanobacteria daily, combined with wastewater recycling, the risk of cyanobacteria blooms is reduced by 60-70%, resulting in significant ecological benefits, reduced aquaculture risks, lower costs, and increased profits.

[0019] Dwarf Vallisneria, a new type of dwarf Vallisneria, grows to a height of no more than 60cm. It is a natural food source favored by crayfish and an important source of plant-based feed. Its most important and unique function is its excellent heat tolerance (most aquatic plants currently used in crayfish farming are not heat-tolerant). During the summer, when aquatic plants are prone to die-off and water quality deterioration, maintaining a good cover of dwarf Vallisneria in ponds can comprehensively inhibit the growth and outbreak of cyanobacteria through multiple mechanisms, including competition for nutrients (core) and light, secretion of algae-inhibiting chemicals, improvement of the aquatic physicochemical environment (stabilizing pH, increasing dissolved oxygen, reducing endogenous release), and promotion of beneficial biological communities. Simultaneously, it provides shade and cooling for crayfish in summer, extends their growth period, promotes crayfish size and gonadal development, and also provides more three-dimensional attachment space for snails. Attached Figure Description

[0020] Figure 1 Diagram of a grid pattern Detailed Implementation

[0021] Detailed Description of the Invention

[0022] A green integrated farming method for snail-shrimp-grass, including

[0023] (1) Construction of a three-dimensional farming system (vertically, an upward three-dimensional space is constructed through aquatic plants; horizontally, a spatial division for the cultivation of Vallisneria natans and the early and late growth of crayfish is constructed through pond enclosure nets, which is conducive to the growth of aquatic plants, crayfish and snails in high-temperature weather)

[0024] In the upper water body of the spatial layout, 100 silver carp fry per mu (667 square meters) are stocked, with a size of 2-4 cm / fish. Practice has proven that this size of fry has the best control effect and has less competition for aquatic feed, and it filters phytoplankton.

[0025] In the middle and lower water layers, crayfish mainly move at the bottom. 4,000 seedlings of the standard size (100 crayfish / jin) are stocked per mu. Elodea is planted from December of the previous year to February of the following year, and Vallisneria natans is planted from February to March to create an underwater three-dimensional space framework (this technology creates an aquatic plant environment for the entire growing season from February to September, increasing the space for crayfish to move in the middle layer of aquatic plants, which helps crayfish avoid predators and cannibalism, and helps improve quality, yield and size).

[0026] Bottom layer: Ringed snails, stocked at 300-500 jin per mu in early March. They feed on leftover food, feces, and other organic debris, as well as attached algae. They can also attach and climb on the underwater forest of Vallisneria natans. The broad, flat leaves of Vallisneria natans are suitable for snails to climb and for algae to attach. Meanwhile, the juvenile snails produced from April to September can be used as live food for crayfish.

[0027] This three-dimensional system maximizes the utilization of organic residues in the water and provides maximum space for the attachment and growth of Bellamy chinensis. By utilizing water resources in layers (upper layer silver carp, middle layer shrimp and grass, lower layer snails and shrimp), spatial complementarity is achieved, resulting in a yield of 800-1000 jin of snails and 200 jin of crayfish per mu, including more than 60 jin of high-quality berried crayfish, which is 150% higher than the traditional method.

[0028] (2) Aquatic plant planting and management techniques

[0029] Variety pairing: One of the core elements of this technique is *Vallisneria natans*, which is heat-tolerant and can cover 55% of the area, serving as the dominant aquatic plant during the high-temperature period from June to September; *Elodea nuttallii*, which thrives primarily in early spring (February to April). (The pairing of *Vallisneria natans* and *Elodea nuttallii* is primarily based on temporal and spatial considerations. *Elodea nuttallii* is a cold-water aquatic plant, suitable for growth in the middle and lower reaches of the Yangtze River from January to May, gradually dying off after the high temperatures in June; while *Vallisneria natans* is a heat-tolerant aquatic plant, showing excellent growth advantages during the high-temperature season from June to September. Aquatic plants in high-temperature conditions play a crucial role in the success or failure of the entire aquaculture, hence this pairing.)

[0030] Planting techniques: Vallisneria natans and Elodea nuttallii should be planted in sections in the pond to avoid Elodea nuttallii covering Vallisneria natans in the early stages and inhibiting its growth.

[0031] Enclose 60% of the pond area with netting for planting Vallisneria natans. In March, select good Vallisneria natans seedlings, wrap the roots of the seedlings into a ball with sticky lake mud, and then throw them directly into the selected water area from a small boat or plant them manually at a spacing of 30 cm x 30 cm.

[0032] Planting Elodea outside the pond enclosure: From December to February of the following year, leave 10-15 cm of water at the bottom of the pond. After disinfecting the pond, transplanting can be carried out. During the planting process, leave a spacing of about 1 meter between rows to facilitate the movement of shrimp and snails.

[0033] Management and maintenance: During February to April, the transitional aquatic plant *Elodea nuttallii* should be used in the pond. From April to May, its growth should be strictly controlled. Before July, every two weeks, cut off the tips of the aquatic plants that have grown above the water surface (judging by the plants emerging above the surface and showing signs of clogging the pond), leaving 30-40 cm above the mud. Clear the waterways to allow space for *Vallisneria natans* to grow. After June, if *Elodea nuttallii* is found to be withering or dying, remove it all promptly to prevent water quality deterioration.

[0034] High-temperature resistant aquatic plant planting and management technology: Through the above series of measures, it can be ensured that ponds using this technology have 50-60% coverage of low-leaved Vallisneria natans during the hot summer days, combined with some Elodea nuttallii, which greatly reduces the incidence of aquatic plant decay and death during the hot summer days in traditional aquaculture mode, thereby ensuring the growth of farmed crayfish during the hot season, and significantly improving their quality and gonadal maturity.

[0035] (3) Ecological regulation of cyanobacteria control and effluent purification

[0036] Ecological regulation: Bellamya can consume cyanobacteria to a certain extent (daily intake accounts for 5% of body weight), and silver carp filter-feed algal spores. This patented technology has the effect of inhibiting cyanobacteria, meaning that cyanobacteria are less likely to break out in ponds.

[0037] Wastewater purification and recycling: Connected with surrounding river crabs and crayfish, it plays a role in partially purifying the pond. During the high-temperature season, if blue-green algae occurs in a certain pond, its wastewater can be directly discharged into the pond with this technology. The first "dwarf Vallisneria + Ring-shaped Snail" synergistic algae control technology is proposed. The constructed "snail-grass" system is used to purify and eliminate blue-green algae, and the purified pond water is recycled.

[0038] Snails consume 3-5% of their body weight in cyanobacteria daily. Combined with wastewater recycling and purification, the risk of cyanobacteria outbreaks is reduced by 60-70%.

[0039] (5) Raising techniques for *Bellamya chinensis*

[0040] ① Seedling selection: Stock 500 catties of *Bambusa ringeri* per mu (approximately 0.067 hectares), including 300-350 catties of medium-sized snails (300-400 snails / catties). Select snails with smooth bodies and free of algae, moss, or other attached organisms. Release the snails evenly along the edge of the pond. The yield per unit area is 120-150% higher than that of traditional snail farming.

[0041] ② Feed formulation: Bellamy chinensis mainly feeds on organic debris and attached algae. After multiple trials and optimizations, the feed formulation is as follows: freshly cooked indica rice + soybean residue (weight ratio 3:1) are evenly mixed and fed immediately.

[0042] ③ Feeding Management: From April to June and September to November (water temperature above 15℃ and below 32℃), every evening at 5 PM (one hour before sunset), evenly scatter the feed along the pond edge at a depth of 40cm. (Studies have found that snails at this water temperature prefer to move and feed in water at a depth of about 40cm. The pond has a sloping embankment, so concentrate the feed around the embankment at a depth of 40cm.) After feeding for the day, if there is still feed left the next morning, appropriately reduce the amount of feed given that day, ensuring that the snails have consumed it all by visual inspection the following morning. In other months, depending on the snails' activity, feed them 2-3 times a week, ensuring that they consume it all within 2-3 days.

[0043] Dissolved oxygen management: The pond adopts a three-dimensional oxygenation method of "bottom micropore oxygenation + surface waterwheel oxygenation". Generally, micropore oxygenation is turned on at night, and waterwheels are turned on for 2-3 hours at noon during the day to maintain dissolved oxygen at 4mg / L at night and 5mg / L during the day.

[0044] Routine prevention: Pay attention to preventing algae and leeches. When the water temperature is above 20℃, regularly (every 7-10 days) apply bottom conditioner and quicklime to adjust the water, improve the bottom, and supplement calcium. On hot days, appropriately increase the water level and maintain water transparency at 40-50cm, where aquatic plants (Vallisneria natans) are visible.

[0045] Example 1

[0046] 1. Pond and aquaculture system design

[0047] (1) Four ponds Figure 1 The ponds are connected in a grid pattern, with U-shaped PVC pipes installed at the bottom of each adjacent pond. The water level in each pond can be automatically controlled by adjusting the height of the pipes.

[0048] Table 1. Grazing and Harvesting Status (2024)

[0049] Free-range farming Harvest (mu) Remark <![CDATA[B1]]> Crayfish seedlings will be released on April 10th, at a rate of 4,000 per mu (approximately 0.067 hectares), with a size of 100 crayfish per jin (approximately 0.5 catties). Snails will be released at a rate of 350 jin per mu in early March, with a size of 300-400 snails per jin. Elodea will be planted in January, and dwarf Vallisneria natans will be transplanted in March. 100 silver carp fry (summer fry) will be released, with a size of 2-4 cm per fish. From July to September, 200 jin of adult shrimp are produced, with 70% of them weighing 35 grams each. From February to April of the following year, 100 jin of shrimp larvae, 800 jin of large-sized snails, and 90 silver carp weighing 50 jin each are produced. Excellent water environment <![CDATA[B2]]> Crayfish fry will be released on April 10th at a rate of 4,000 fry per mu (approximately 0.067 hectares), with a size of 100 fry per jin (approximately 0.5 kg). Adult crayfish from the previous year will be retained from the pond. Elodea will be transplanted in February. 100 silver carp and bighead carp fry (summer fry) will also be planted. From July to September, 120 catties of adult shrimp were produced, with 60% of them weighing 20 grams each. From February to April of the following year, 150 catties of shrimp larvae and 180 silver carp and bighead carp were produced, weighing 100 catties. In early August, Elodea died, causing a blue-green algae bloom and resulting in the loss of some shrimp. <![CDATA[B3]]> Crayfish seedlings will be released on April 10th at a rate of 4,000 per mu (approximately 0.067 hectares), with a size of 100 crayfish per jin (approximately 0.5 catties). Snails will be released at a rate of 350 jin per mu in early February, with a size of 300-400 snails per jin. Elodea will be transplanted in February. 100 silver carp and bighead carp fry (summer fry) each will be released. From July to September, 130 jin of adult shrimp were produced, with 60% of them weighing 20 grams each. From February to April of the following year, 120 jin of shrimp larvae were produced; 500 jin of snails were produced, with small sizes; and 90 silver carp weighed 50 jin each. In early August, some Elodea algae withered, blue-green algae appeared, and some shrimp and snails were lost; <![CDATA[B4]]> Conventional farming of grass carp, silver carp, bighead carp, and bream involves stocking 2,500 fish per mu (approximately 0.16 acres). 3300 jin (1650 catties), normal breeding The pool water was normal, but a small amount of blue-green algae appeared in August.

[0050] Note: In February, B1 was thoroughly cleaned with bleaching powder. One week later, the pond was filled with water, and the pond was cleaned again to disinfect any remaining wild animals and overwintering crayfish. Quicklime was then applied and the pond was left to dry for a week before transplanting / planting Elodea rhizomes and dwarf Vallisneria rhizomes in different areas. See the table above for the species, sizes, and quantities to be stocked.

[0051] 2. Breeding and Management Process

[0052] The initial management methods for ponds B1, B2, and B3, including the timing of planting aquatic plants and stocking shrimp larvae, were basically the same. The feed consisted mainly of formulated feed with 36% protein. Pond B1 was fed fermented soybean cake and soybean residue twice a week. In May, if *Elodea nuttallii* was growing vigorously, the tops of the plants were regularly trimmed to control its growth and to clear the waterways. During the prolonged high temperatures in August, *Elodea nuttallii* gradually declined, and blue-green algae blooms began, especially in pond B2. Water was allowed to circulate between ponds B2 and B1. A water pump drew water from the upper layer of B2 to B1, and the lower layer of B1 flowed back to B2 through a U-shaped pipe, creating a cycle. Blue-green algae gradually appeared on the surface of pond B1, but the level was kept low enough to allow the *Vallisneria natans* to receive sunlight. Lactic acid bacteria were sprayed simultaneously in both ponds. The blue-green algae gradually disappeared after a week. If the water volume was insufficient, water from pond B4 was used as a supplement. The same method of circulating and purifying water from pond B3 was used in conjunction with pond B1. The "snail + Vallisneria natans + silver carp" all-biological method created by B1 during the summer effectively controlled the cyanobacterial bloom.

[0053] 3. Data, Results and Analysis

[0054] Economic benefits: Average yield per mu is 5,000-8,000 yuan, and breeding costs are reduced by 30%; Environmental benefits: TN / TP removal rate in wastewater exceeds 60%, which meets the "Freshwater Aquaculture Wastewater Discharge Standard" (GB / T 32725-2016); Social benefits: Provides off-peak crayfish (July-September), increasing the unit price by 20%-30%.

[0055] Table 2: Costs and Benefits of Different Free-Range Farming Models

[0056] Input costs (per mu) Output (per mu) Profit (per mu) <![CDATA[B1]]> Crayfish seedlings, 400 yuan; snails, 350 jin, 600 yuan; dwarf Vallisneria natans transplanted at the end of March, 300 yuan; silver carp fry (summer fry), 10 yuan; labor, 1000 yuan; feed, 1200 yuan; electricity, 200 yuan; water conditioning microbial preparation: 0 yuan; total: 3710 yuan 200 jin of adult shrimp (July-September), 70% of which are 35 grams each, cost 8000 yuan; 100 jin of shrimp larvae (February-April of the following year), cost 1000 yuan; 1000 jin of large snails, cost 1500 yuan; 90 silver carp (50 jin), cost 100 yuan; Total: 10600 yuan 6890 <![CDATA[B2]]> Crayfish seedlings, 400 yuan; Elodea nuttallii transplanted at the end of February, 200 yuan; silver carp and bighead carp fry, 20 yuan; labor, 1000 yuan; feed, 1500 yuan; electricity, 200 yuan; water conditioning microbial preparations, etc., 400 yuan; total: 3720 yuan; 150 jin of adult shrimp (July-September), 60% of which are 20g / shrimp, cost 3000 yuan. 150 jin of shrimp larvae (February-April of the following year) cost 1500 yuan. 180 silver carp and bighead carp (100 jin) cost 300 yuan. Total: 4800 yuan. 1080 <![CDATA[B3]]> Crayfish seedlings, 400 yuan; snails, 600 yuan; Elodea, 200 yuan; silver carp and bighead carp fry, 20 yuan; labor, 1000 yuan; feed, 1500 yuan; electricity, 200 yuan; water conditioning microbial preparations, etc., 200 yuan; total: 3920 yuan 150 jin of adult shrimp (July-September), 60% of which are 20g / shrimp, cost 3000 yuan; 120 jin of shrimp larvae (February-April of the following year), cost 1200 yuan; 1000 jin of snails (small size), cost 1500 yuan; 90 silver carp (50 jin), cost 100 yuan; Total: 5800 yuan 1880 <![CDATA[B4]]> Standard breeding costs for grass carp, silver carp, bighead carp, and bream fry: 2000 yuan; feed cost: 15000 yuan; labor cost: 500 yuan; electricity cost: 280 yuan; water conditioning microorganisms, etc.: 200 yuan; total: 17980 yuan. 3300 jin (1650 catties), normal breeding; total cost: 19800 yuan. 1820

Claims

1. A green three-dimensional farming method for snail-shrimp-grass, characterized in that, include: Silver carp are raised in the upper and middle layers of the pond, with 80-150 silver carp fry per mu (approximately 0.067 hectares) stocked, each fry measuring 2-4 cm. In early April, 3,000-5,000 crayfish of 80-120 crayfish per acre are stocked in the middle and lower layers of the pond. Elodea is planted from December of the previous year to February of the following year, and Vallisneria natans is planted in February and March to construct an underwater three-dimensional space framework. Bellamy chinensis is raised in the bottom water of the pond from December of the previous year to March of the following year, at a rate of 300-500 jin per acre. Bellamy chinensis feeds on uneaten food, feces, and other organic debris and attached algae, and can also attach to and climb on the underwater forest of Vallisneria natans.

2. The method according to claim 1, characterized in that, The silver carp fry are 2-4 cm in length per fish, and the crayfish fry are 80-120 fish per pound.

3. The method according to claim 1, characterized in that, 300-500 catties of ringed snails are released per mu, with a size of 300-400 snails per catty.

4. The method according to claim 3, characterized in that, The feed formula for the ringed snail is freshly cooked indica rice and soybean residue mixed evenly at a weight ratio of 3:

1. It should be prepared and fed immediately.

5. The method according to claim 3, characterized in that, From April to June and from September to November, feed the snails evenly along the edge of the pond at a depth of 40cm every evening from 5 pm to 6 pm. If there is still food left the next morning, reduce the amount of food given that day so that it can be seen by the naked eye that the snails have eaten it all the next morning. In other months, depending on the snails' activity, feed them 2-3 times a week, with the goal of eating it all within 2-3 days.

6. The method according to claim 1, characterized in that, Dwarf Vallisneria and Elodea are planted in sections in the pond: 50%-60% of the pond area is enclosed by a net for planting Dwarf Vallisneria, and Elodea is planted outside the net.

7. The method according to claim 1, characterized in that, Elodea is the transitional aquatic plant in the pond from February to April. During April and May, the growth of Elodea should be strictly controlled. Before the high temperature in July, the tops of the plants that have grown above the water surface should be cut every two weeks to leave 30-40 cm above the mud. This will clear the waterways and leave space for the growth of Vallisneria. After June, if Elodea is found to be decaying or dying, it should be removed in time to prevent the water quality from deteriorating.

8. The method according to claim 1, characterized in that, The pond adopts a three-dimensional aeration method of "bottom micropore aeration + surface waterwheel aeration". Generally, the micropore aeration is turned on at night, and the waterwheel is turned on for 2-3 hours at noon during the day to maintain the dissolved oxygen at 3.5-4.5mg / L at night and 5mg / L during the day.

9. The method according to claim 1, characterized in that, Pipelines are installed to connect with surrounding crab ponds and crayfish ponds. If blue-green algae blooms occur in a nearby pond, its wastewater can be directly discharged into the pond described in claim 1 for purification and recycling.

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