A feeding and water quality coordinated regulation method for longsnout catfish land-based barrel zero water change culture

Abstract

The application discloses a feeding and water quality synergic regulation method for Leiocassis longirostris land-based barrel zero water changing culture, and relates to the technical field of aquaculture. Before releasing fry, the method inoculates mature biological floc concentrate into the water body of the land-based barrel culture, adds carbon source for aeration activation culture, and establishes a steady-state biological floc water body environment; after starting the culture, the method fixedly feeds special compound feed for Leiocassis longirostris four times a day; the method detects total ammonia nitrogen concentration, nitrite nitrogen concentration and pH value at fixed time every day; when monitoring the pH value of the culture water is less than 7.2, or the total ammonia nitrogen concentration is greater than 1.0 mg / L for two consecutive days, or the nitrite is greater than 0.5 mg / L for two consecutive days, the method supplements red sugar and glucose (3:1) compound carbon source into the culture water according to the nitrogen input corresponding to the feeding amount of the day. The yield and survival rate of the Leiocassis longirostris culture adopting the method are better than those of the traditional water changing culture mode, harmful water quality indexes such as ammonia nitrogen and nitrite are lower than those of the traditional water changing culture mode, and zero water changing healthy culture is realized.

Description

Technical Field

[0001] This invention relates to the field of aquaculture technology, and in particular to a method for the coordinated control of feeding and water quality in land-based cylindrical aquaculture of long-snout catfish with zero water exchange. Background Technology

[0002] Longsnout catfish is a high-value freshwater fish species with tender flesh, no intramuscular bones, and high nutritional value, making it popular in the market and possessing great potential for aquaculture promotion. Traditional pond aquaculture requires large land areas, consumes a lot of water, is difficult to control diseases, and is significantly affected by environmental climate. Land-based cylindrical aquaculture, as a new intensive aquaculture model, has advantages such as land saving, water saving, and strong controllability; however, wastewater treatment remains a challenge. Achieving true "zero water exchange" aquaculture hinges on how to efficiently treat metabolic waste such as uneaten feed and feces produced by the aquatic animals themselves, preventing the accumulation of toxic substances such as ammonia nitrogen and nitrite.

[0003] Existing land-based cylindrical aquaculture systems rely heavily on large-scale water exchanges, physical filtration, or microbial filters for water quality management. However, these systems are complex to construct, energy-intensive, and costly to maintain. Biofloc technology is a water treatment technique that promotes the growth of heterotrophic bacteria in the water by adding organic carbon sources, converting inorganic nitrogen into bacterial protein that can be ingested by farmed animals. However, there is no mature solution for applying this technology to the intensive land-based cylindrical aquaculture of catfish, especially under zero-water-exchange conditions. In particular, the synergy between feeding strategies and carbon source addition is crucial. Improper feeding can lead to peak-valley fluctuations in waste, while rigid carbon source addition cannot cope with real-time water quality changes. This disconnect between the two can easily lead to the collapse of the aquaculture system and the death of farmed fish.

[0004] Therefore, the key to achieving efficient, zero-water-change aquaculture of long-snout catfish in land-based cylindrical tanks lies in finding an integrated method that matches biofloc technology with precise feeding and water quality control.

[0005] Therefore, those skilled in the art are dedicated to developing a feeding and water quality coordination method that matches biofloc technology, in order to achieve efficient land-based cylindrical aquaculture of long-snout catfish with zero water exchange. Summary of the Invention

[0006] In view of the above-mentioned deficiencies of the prior art, the technical problem to be solved by the present invention is to develop a method for the coordinated regulation of feeding and water quality in land-based cylindrical aquaculture of long-snout catfish with zero water exchange.

[0007] To achieve the above objectives, this invention provides a method for the coordinated regulation of feeding and water quality in land-based cylindrical aquaculture of long-snout catfish with zero water exchange.

[0008] Furthermore, a method for coordinated feeding and water quality control in land-based cylindrical aquaculture of *Catfish fasciatus* with zero water exchange is achieved through four coordinated processes: targeted cultivation of bioflocs in the early stage, timed and quantitative feeding during aquaculture, precise carbon source supplementation linked to nitrogen load in water quality, and daily trace bottom discharge and floc management. The entire process does not involve replacing the main aquaculture water body. Specifically, it includes the following steps: S1. Pre-breeding biofloc directional culture: Before stocking, mature biofloc concentrate is inoculated into the land-based cylindrical aquaculture water body, and dual carbon sources are added for aeration and activation culture. Heterotrophic bacteria that degrade uneaten feed and feces of long-snout catfish are directionally cultured and enriched to quickly establish a stable biofloc water body environment adapted to the metabolic characteristics of long-snout catfish. S2. Timed and quantitative feeding for aquaculture: After the start of aquaculture, feed the long-snout catfish with high-protein compound feed at fixed times and in a balanced manner 4 times a day, with the interval between two consecutive feedings controlled at 6 hours; dynamically match the daily feeding rate based on the benchmark that there is no uneaten feed within 0.25 hours of a single feeding, and adapt to the day and night segmented feeding rhythm of the long-snout catfish. S3. Precise Carbon Source Regulation Linked to Nitrogen Load in Water Quality: Water samples are collected from the aquaculture water at fixed times every day to test the total ammonia nitrogen concentration, nitrite nitrogen concentration, and pH value. When the pH of the aquaculture water is <7.2, or the total ammonia nitrogen concentration is >1.0 mg / L for two consecutive days, or the nitrite concentration is >0.5 mg / L for two consecutive days, 12 to 14 times the amount of carbon source is added to the aquaculture water based on the total nitrogen input of all feeds fed that day, to precisely supplement the carbon source and maintain the stability of the floc system. S4. Micro-bottom discharge and floc density control: Daily timed short-term bottom discharge to maintain stable floc concentration in the water, discharge excess aging flocs and solid excrement, and replenish with an equal amount of aerated fresh water after discharge, combined with transparency control to inhibit excessive floc proliferation.

[0009] Furthermore, in step S1, 1-2 liters of mature long-snout catfish-specific biofloc concentrate are inoculated per cubic meter of water.

[0010] Further, in step S1, the dual carbon source is a mixture of brown sugar and glucose in a mass ratio of 3:1; the amount of carbon source added at one time is 20-50 g / m³. 3 .

[0011] Furthermore, in step S2, the daily feeding rate is determined based on the fact that the feed is basically consumed within 0.25 hours after a single feeding, and is controlled to be 6.0% to 8.0% of the total fish mass.

[0012] Furthermore, in the early stage of aquaculture (body weight < 80g), the daily feeding rate is controlled at 6.0% of the total body weight of the fish; in the later stage of growth (body weight ≥ 80g), the daily feeding rate is increased to 7.0-8.0%.

[0013] Furthermore, in step S2, the daily feeding times are 2:00, 8:00, 14:00 and 20:00, with feeding occurring once every 6 hours.

[0014] Furthermore, in step S2, the stocking density of long-snout catfish is fixed at 50 individuals / m². 3 The land-based cylindrical tank is continuously aerated to ensure that the feed is completely consumed within 0.25 hours after each feeding, with no residual feed accumulating.

[0015] Furthermore, in step S4, the micro-bottom discharge and floc transparency are controlled in synergy: the bottom drain valve is opened for 20-30 seconds every morning to discharge excess flocs and solid waste that have settled, with the discharged water volume accounting for 0.1-0.2% of the total volume. Then, an equal amount of chlorine-free fresh water that has been aerated is added to the original water level. Throughout the process, the water body is maintained at a light yellowish-brown color and the water transparency is stable at 25-30cm, avoiding the flocs from becoming too sparse and unstable or too concentrated and lacking oxygen.

[0016] In a preferred embodiment 1 of the present invention, the feeding and water quality control process of land-based cylindrical aquaculture of long-snout catfish with zero water exchange is described in detail.

[0017] Technical effects: 1. This invention couples 6-hour interval feeding with dynamic carbon source regulation of biofloc technology. By uniformly feeding four times a day and night, it suppresses the concentrated release of metabolic waste such as uneaten fish feed and feces. The carbon-to-nitrogen ratio is dynamically adjusted based on real-time indicators of water pH, total ammonia nitrogen, and nitrite, continuously providing substrates for heterotrophic bacteria and achieving in-situ degradation of inorganic nitrogen. This method enables zero water exchange throughout the entire aquaculture process, eliminates the need for external water treatment equipment, achieves a water saving rate of over 90%, maintains total ammonia nitrogen and nitrite levels within safe ranges over the long term, minimizes water quality fluctuations, and significantly improves the operational stability of the aquaculture system.

[0018] 2. The method of this invention fixes feeding times at six-hour intervals: 02:00, 08:00, 14:00, and 20:00. This timing is independent of season and weather, precisely matching the diurnal feeding rhythm of farmed fish, balancing the daily feeding and excretion load, reducing short-term water quality shocks caused by concentrated feeding, and providing a continuous and stable nitrogen source for the biofloc system. This method effectively reduces individual differences in fish growth, improves feed utilization, and simultaneously inhibits nighttime nitrogen accumulation, reducing the risk of nighttime water quality deterioration, thus contributing to the stable operation of the biofloc system.

[0019] 3. The method of this invention sets a carbon supplementation trigger threshold as pH < 7.2, total ammonia nitrogen exceeding 1.0 mg / L for two consecutive days, or nitrite exceeding 0.5 mg / L for two consecutive days. When any of these threshold conditions are triggered, a composite carbon source of brown sugar and glucose at a mass ratio of 3:1 is used for targeted supplementation. A decrease in pH, and excessive total ammonia nitrogen and nitrite levels, are used as signals to determine carbon-nitrogen ratio imbalance and insufficient heterotrophic bacteria activity. Precise carbon supplementation can rapidly optimize the carbon-nitrogen ratio in the water, promote the conversion of inorganic nitrogen into bacterial proteins, and simultaneously stabilize the water pH within the suitable range of 7.2–8.0. This method can improve carbon source utilization efficiency, reduce the surge in oxygen consumption caused by indiscriminate carbon supplementation, and enhance the removal capacity of total ammonia nitrogen and nitrite, thus helping to reduce the incidence of aquaculture diseases.

[0020] 4. This invention provides a standardized cultivation process for mature bioflocs. During the system construction stage before stocking, or when the water transparency is greater than 30cm during cultivation, the concentration is 1-2 L / m³. 3 Add the floc concentrate along with initial carbon source replenishment. Utilizing the highly active heterotrophic bacteria inherent in the mature flocs, they can rapidly colonize the aquaculture water and form a dominant microbial community, accelerating the activation of the water's in-situ purification function. This process can shorten the start-up and acclimatization period of the biofloc system, reduce the risk of water quality deterioration in the early stages of aquaculture, and facilitate the rapid transition of zero-water-change aquaculture systems to a stable operating state.

[0021] The following will further explain the concept, specific structure and technical effects of the present invention in conjunction with the embodiments and accompanying drawings, so as to fully understand the purpose, features and effects of the present invention. Attached Figure Description

[0022] Figure 1 This is a flowchart illustrating the overall process flow of the method of the present invention. Detailed Implementation

[0023] The following describes several preferred embodiments of the present invention to make its technical content clearer and easier to understand. The present invention can be embodied in many different forms, and the scope of protection of the present invention is not limited to the embodiments mentioned herein.

[0024] The land-based cylindrical container used in this invention is equipped with a bottom drain valve and a 24-hour oxygenation system (consisting of a microporous oxygenation disc and an oxygenator). The container is cleaned and disinfected before the experiment.

[0025] Example 1

[0026] 1. Experimental Design

[0027] From March 26, 2025 to August 2, 2025, a 130-day comparative culture experiment was conducted at the No. 3 culture shed of the Fengxian Research Base of the Shanghai Fisheries Research Institute. Longsnout catfish fry with an average weight of 57.63±11.11g and an average body length of 15.98±1.13cm were cultured in 45-cubic-meter land-based circular canvas tanks at a stocking density of 50 fish / m³. 3 .

[0028] Setting up experimental and control groups: Experimental group (biofloc group): No water change, feed the long-snout catfish special high-protein compound feed 4 times a day at fixed times, and strictly control the interval between two consecutive feedings to 6 hours, feeding time points are 02:00, 08:00, 14:00 and 20:00.

[0029] Control group (traditional water exchange aquaculture mode): water was changed once every 7 days (two-thirds of the water was changed each time), and feed was given twice a day at 08:00 and 20:00.

[0030] Both groups received the same daily feed amount, but the feeding rate was controlled at 6.0-8.0% of the total fish body weight. The daily feeding rate was dynamically adjusted based on the benchmark of no uneaten feed within 0.25 hours after a single feeding, adapting to the diurnal feeding rhythm of the long-snout catfish. The aquaculture system was equipped with bottom nano-aeration discs and micro-pore aerators to maintain dissolved oxygen in the range of 6.71 mg / L-8.35 mg / L.

[0031] 2. Feeding Management

[0032] Both groups were fed a timely supply of specialized feed for long-snout catfish (slow-sinking pellets, purchased from Tongwei Co., Ltd.). The daily feeding rate was 6.0% during the initial rearing period, with adjustments made based on observations 0.25 hours after each feeding. As the fish grew, their body weight was reassessed every 7 days, and the daily feed amount was adjusted accordingly, maintaining a daily feeding rate of 6.0–8.0% of the total fish weight.

[0033] 3. Water quality testing and control

[0034] (1) Construction of biofloc system

[0035] Three days before stocking, inoculate 30 liters of mature floc concentrate from a stable biofloc culture tank into a land-based cylindrical container containing 40 cubic meters of water. This mature floc concentrate is a high-concentration suspension obtained from a stable biofloc culture system through sedimentation and concentration; its core consists of mature floc particles (yellowish-brown, 100–200 μm) with stable bacterial community structure, high activity, and good settling properties. It contains heterotrophic bacteria, nitrifying / denitrifying bacteria, protozoa, and extracellular polymers, which can rapidly degrade total ammonia nitrogen / nitrite, are suitable for aquaculture water, and can establish a stable floc system 3–5 days after inoculation. Pre-stocking inoculation can quickly start the biofloc system, shorten the water conditioning cycle, stabilize water quality, and reduce the risk of disease.

[0036] After inoculation, add 12kg of brown sugar and 4kg of glucose at once (estimated based on 1-2 liters of floc concentrate per cubic meter of water). Turn on the aeration equipment for aeration and cultivation. The cultivation conditions are: a stable system can be established after 3-5 days of cultivation, with the temperature maintained at around 26℃ and continuous strong aeration for 20-25 hours.

[0037] The initial water quality indicators for aquaculture were: total ammonia nitrogen 0.13 mg / L, nitrite nitrogen 0.028 mg / L, and pH 7.84.

[0038] (2) Routine water quality testing

[0039] After the aquaculture began, water samples were collected daily at 8:00 AM to test water quality indicators. Each sampling was conducted at the same location in the circular pond, with a sample size of 500 mL taken 30 cm above the water surface.

[0040] Detection methods: Total ammonia nitrogen (TAN) was determined using the phenol-hypochlorite method; nitrite nitrogen (NO) was determined... 2- N was determined using the diazo-azo colorimetric method; pH was measured in real-time using a YSI instrument made in the USA.

[0041] (3) Water quality control

[0042] On the 7th day of culture, monitoring revealed that in the traditional water exchange culture mode (control group), the total ammonia nitrogen concentration rose to 1.03 mg / L, the nitrite concentration rose to 2.09 mg / L, and the pH dropped to 7.13. In contrast, the biofloc group showed an ammonia nitrogen concentration of 0.29 mg / L, a nitrite concentration of 0.27 mg / L, and a pH of 7.38. The total ammonia nitrogen and nitrite nitrogen in the biofloc group were significantly lower than those in the traditional water exchange culture mode, while the pH was significantly higher. Water exchange measures were immediately implemented for the traditional water exchange culture mode, and thereafter, the traditional water exchange culture mode was to be operated on a regular basis every 7 days, with two-thirds of the water replaced each time.

[0043] On the 14th day of rearing, monitoring revealed that the total ammonia nitrogen concentration in the biofloc group (experimental group) rose to 1.21 mg / L, the nitrite concentration rose to 1.56 mg / L, and the pH dropped to 7.1. The corresponding nitrogen input was immediately calculated based on the daily feed intake, and a carbon source (a mixed solution of brown sugar and glucose) was added.

[0044] The specific method for supplementing carbon sources is as follows: When the total ammonia nitrogen and nitrite in the water exceed the standard and the pH is low, firstly calculate the nitrogen input load of the feed based on the daily feeding amount, and calculate the total daily nitrogen input with a crude protein nitrogen content of 16%; then, based on the appropriate control standard of C / N ratio of 12~14 for biofloc culture, determine the target C / N ratio in combination with the degree of nitrogen pollution in the water, and then calculate the total amount of organic carbon that needs to be supplemented to the water. Calculate the dosage of compound carbon source according to a fixed ratio of brown sugar and glucose, and apply it by spraying. This precise carbon supplementation improves the C / N ratio of the water, promotes the large-scale reproduction of heterotrophic microorganisms, enhances the assimilation and denitrification efficiency of bioflocs, rapidly degrades ammonia nitrogen and nitrite in the water, and simultaneously adjusts and buffers the pH of the water, restoring and stabilizing the pH of the aquaculture water to a suitable range.

[0045] After supplementation and continuous monitoring, on the 3rd day, the total ammonia nitrogen concentration dropped to below 0.22 mg / L, the nitrite concentration dropped to 0.33 mg / L, and the pH rose back to 7.75.

[0046] In subsequent aquaculture, whenever the total ammonia nitrogen shows a continuous upward trend (>1.0 mg / L), the nitrite concentration shows a continuous upward trend (>0.5 mg / L), and the pH continuously decreases to less than 7.2, carbon sources should be supplemented according to the above principle to make the carbon-nitrogen ratio 12-14:1.

[0047] 4. Daily Management: Every morning, open the bottom drain valve for 20-30 seconds to remove excess flocculation and solid waste (the discharged water volume accounts for approximately 0.1-0.2% of the total volume). Then, add an equal amount of aerated fresh water to the original water level. Maintain the water color as a light yellowish-brown and the transparency at 25-30 cm. Aerate for 24 hours to maintain dissolved oxygen >5 mg / L.

[0048] 4. Aquaculture Results: After 130 days of rearing, the final average body weight, survival rate, and feed conversion ratio of the two groups were statistically analyzed. The experimental results are shown in Table 1. Table 1

[0049] Results Analysis: Table 1 shows that the average body weight of the experimental group increased by 11.1% compared to the control group, the survival rate increased by 8.84%, and the feed conversion ratio decreased by 0.32. This indicates that the yield and survival rate of the biofloc culture group were superior to those of the traditional water exchange culture model. Furthermore, the water quality indicators (ammonia nitrogen and nitrite concentrations) of the biofloc culture group were lower than those of the traditional water exchange culture model during the culture period. No diseases caused by water quality deterioration occurred throughout the entire culture cycle, and no large-scale water exchange was required, achieving healthy culture with zero water exchange.

[0050] The preferred embodiments of the present invention have been described in detail above. It should be understood that those skilled in the art can make numerous modifications and variations based on the concept of the present invention without creative effort. Therefore, all technical solutions that can be obtained by those skilled in the art based on the concept of the present invention through logical analysis, reasoning, or limited experimentation on the basis of existing technology should be within the scope of protection defined by the claims.

Claims

1. A method for synergistic control of feeding and water quality in terrestrial cylindrical tank aquaculture of *Cetacea longsnout* with zero water exchange, characterized in that, The process is completed through four coordinated steps: targeted cultivation of bioflocs in the early stage, timed and quantitative feeding during aquaculture, precise carbon source supplementation linked to water quality nitrogen load, and daily trace bottom discharge and floc management, all without replacing the main aquaculture water body. Specifically, it includes the following steps: S1. Pre-breeding biofloc directional culture: Before stocking, mature biofloc concentrate is inoculated into the land-based cylindrical aquaculture water body, and dual carbon sources are added for aeration and activation culture. Heterotrophic bacteria that degrade uneaten feed and feces of long-snout catfish are directionally cultured and enriched to quickly establish a stable biofloc water body environment adapted to the metabolic characteristics of long-snout catfish. S2. Timed and quantitative feeding for aquaculture: After the start of aquaculture, feed the long-snout catfish with high-protein compound feed at fixed times and in a balanced manner 4 times a day, with the interval between two consecutive feedings controlled at 6 hours; dynamically match the daily feeding rate based on the benchmark that there is no uneaten feed within 0.25 hours of a single feeding, and adapt to the day and night segmented feeding rhythm of the long-snout catfish. S3. Precise Carbon Source Regulation Linked to Nitrogen Load in Water Quality: Water samples are collected from the aquaculture water at fixed times every day to test the total ammonia nitrogen concentration, nitrite nitrogen concentration, and pH value. When the pH of the aquaculture water is <7.2, or the total ammonia nitrogen concentration is >1.0 mg / L for two consecutive days, or the nitrite concentration is >0.5 mg / L for two consecutive days, 12 to 14 times the amount of carbon source is added to the aquaculture water based on the total nitrogen input of all feeds fed that day, to precisely supplement the carbon source and maintain the stability of the floc system. S4. Micro-bottom discharge and floc density control: Daily timed short-term bottom discharge to maintain stable floc concentration in the water, discharge excess aging flocs and solid excrement, and replenish with an equal amount of aerated fresh water after discharge, combined with transparency control to inhibit excessive floc proliferation.

2. The feeding and water quality synergistic control method for land-based cylindrical zero-water-change aquaculture of long-snout catfish as described in claim 1, wherein in step S1, 1-2 liters of mature long-snout catfish-specific biofloc concentrate are inoculated per cubic meter of water.

3. The feeding and water quality synergistic control method for land-based cylindrical tank aquaculture of *Cetus fasciatus* with zero water exchange as described in claim 1, wherein in step S1, the dual carbon source is a mixture of brown sugar and glucose in a mass ratio of 3:1; the amount of carbon source added at one time is 20-50 g / m³. 3 .

4. The feeding and water quality synergistic control method for land-based cylindrical zero-water-change culture of long-snout catfish as described in claim 1, wherein in step S2, the daily feeding rate is determined based on the fact that the feed is basically consumed within 0.25 hours after a single feeding, and is controlled to be 6.0 to 8.0% of the total fish mass.

5. The feeding and water quality co-regulation method for land-based cylindrical zero-water-change culture of long-snout catfish as described in claim 4, wherein in the early stage of culture, the fish body weight is less than 80 grams, and the daily feeding rate is controlled at 6.0% of the total fish body weight; in the later stage of culture, the fish body weight is not less than 80 grams, and the daily feeding rate is increased to 7.0-8.0%.

6. The feeding and water quality synergistic control method for land-based cylindrical tank zero-water-change aquaculture of long-snout catfish as described in claim 1, wherein in step S2, the daily feeding times are 2:00, 8:00, 14:00 and 20:00, and feeding is carried out once every 6 hours.

7. The feeding and water quality co-regulation method for land-based cylindrical tank aquaculture of *Catfish brevicus* with zero water exchange as described in claim 1, wherein in step S2, the culture density of *Catfish brevicus* is fixed at 50 individuals / m². 3 The land-based cylindrical tank is continuously aerated to ensure that the feed is completely consumed within 0.25 hours after each feeding, with no residual feed accumulating.

8. The feeding and water quality synergistic control method for land-based cylindrical zero-water-change aquaculture of *Cyprinus longsnoutus* as described in claim 1, wherein in step S4, the micro-bottom discharge and floc transparency are synergistically controlled: the bottom drain valve is opened for 20-30 seconds every morning to discharge excess flocs and solid waste that have settled, with the discharged water volume accounting for 0.1-0.2% of the total volume, and then an equal amount of chlorine-free fresh water that has been aerated is added to the original water level, maintaining the water body in a light yellowish-brown color and the water body transparency at a stable 25-30cm throughout the process, avoiding the flocs from becoming too sparse and unstable or too concentrated and lacking oxygen.

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