Water quality management of Chinese sawtooth rice shrimp aquaculture
The Chinese serrated rice shrimp (Neocaridinadenticulate) belongs to the phylum arthropods, crustaceans, decapods, gymnodydylidae, and the genus Neocaridinadenticulate. This species has strong environmental adaptability, is widely distributed in the freshwater waters of Asia, and has obvious regional differences in morphology and body color. Cherry blossom shrimp, cultivated by screening red mutants, has been a new favorite of aquarium enthusiasts since 2003 and has taken a place in ornamental shrimp. Since then, more than a dozen strains have been cultivated, such as extreme fire shrimp, golden rice shrimp, xiangjishi, bloody Mary shrimp, blue velvet shrimp and glass shrimp. Because of its beautiful colors and easy feeding, it is favored by enthusiasts. In addition to its ornamental value, Chinese sawtooth rice shrimp also has the characteristics of short generation cycle, large eggs and high survival rate of experimental subjects, which is an ideal scientific research material. Since 2015, the author has been cultivating Chinese sawtooth rice shrimp (hereinafter referred to as rice shrimp for convenience). Rice shrimp farming focuses on water quality control. This is a task with a lot of work and many considerations. Now summarize the experience of water quality management and provide reference for the majority of rice and shrimp lovers.
First, water temperature control
The most suitable water temperature for rice shrimp is 20 to 25 °C. Adults are 2 to 3 cm long and belong to small ornamental shrimp, suitable for culture in glass tanks. For indoor aquaculture, the water temperature is better controlled. In the hot summer, air conditioning can be used to cool down, but it is particularly important to note that the water temperature cannot be determined according to the temperature displayed by the air conditioner. The reasons are as follows, the first cold air through the air propagation, by the influence of hot air to produce a certain loss, and can not reach the water body 100% ; the second when the water body is very large, the temperature of different levels of water body is different, the author has measured the water temperature in different locations of the large aquarium, the temperature difference is about 1 ° C (including the water temperature caused by the heat production of the equipment). The overall water temperature of the small aquarium is relatively uniform. Therefore, the thermometer recommends using a long strip to reach the lower layer of the water body, or fixing the thermometer to the lower layer of the water body. In the cold winter, indoor farming adopts intelligent heating rods, which are fixed to the middle and lower water layers, and a layer of isolation cover is put on to prevent rice shrimp from crawling on the heating rods and causing burns or damage to the heating rods. Outdoor aquaculture, due to cyclical day and night changes and seasonal changes, has a certain interference with water temperature control. However, we can also adopt the principle of differences in water temperature at different levels, by increasing the depth of the water body, adding a shade net or insulation film and controlling the flow rate of the water body to control the temperature. In winter, if necessary, a heating rod with greater power can be added. However, outdoor aquaculture cannot blindly control the temperature at a certain point, but control the amount of temperature change in different time periods, which can avoid causing physiological stress. Special attention is paid to the fact that when changing the water, the difference in water temperature should not be too large, so as to avoid the death of the rice shrimp from stress shock.
Second, dissolved oxygen control
The monitoring and management of dissolved oxygen is also overlooked in the rice shrimp feeding process. The main reason is that most enthusiasts use continuous circulation of filtered water equipment to increase dissolved oxygen, which can reach more than 6 mg/L under normal conditions. However, when the light is turned off for a long time, the expected and unintended circulating water flow is stopped due to operation or power outage, or the water temperature rises due to strong light exposure and waste heat of equipment and equipment, the dissolved oxygen will be reduced. In addition, plants in the water body will consume a lot of dissolved oxygen in dark conditions; continuous rain and continuous sweltering heat will lead to a decline in dissolved oxygen in the water body; when adding microbial preparations, oxygen consumption will increase rapidly, endangering the survival of rice shrimp. The author recommends properly controlling the temperature, paying attention to the changes in dissolved oxygen and the growth of algae before and after drug application, while appropriately increasing the circulation and water exchange of water, and regularly maintaining and updating the biological filter bed, which can help the dissolved oxygen to be within a safe range, so as to avoid the phenomenon that rice shrimp is in a state of long-term stress and leads to growth retardation, shock and even hypoxia death.
For professional breeders, in addition to the necessary aeration equipment, it is also necessary to prepare oxygenators, just in case. In the case of severe hypoxia, a large number of rice shrimp will swim along the water surface wall, at this time the opening of the aerator can not solve the urgent need, and the oxygenator can be evenly sprinkled throughout the pool, rapid oxygenation, to avoid the possibility of a large number of deaths caused by the lack of oxygen of rice shrimp.
Third, the control of inorganic salts
Calcium and magnesium ions are a constant element in cultured water bodies, which have an important impact on the growth and development of rice shrimp. Calcium and magnesium ions will participate in the physiological regulation of various enzymes in rice shrimp. Studies have shown that the addition of a certain concentration of calcium and magnesium ions to water can promote the molting and growth of shrimp, in which calcium ions are directly involved in the calcification of carapace. And different concentrations of calcium ions affect the growth rate and energy balance of shrimp. Since rice shrimp do not have the ability to store calcium ions, a large amount of calcium ions need to be replenished after molting. When the total calcium and magnesium ions are 105 mg/l, and the mass ratio of calcium and magnesium ions is 1:3, the viability and survival rate of rice shrimp can be significantly improved. For the control of calcium and magnesium ion content, the author uses a calcium magnesium ion concentration analyzer to determine the ion concentration in the water body, and then calculates the content that needs to be supplemented according to the size of the water body, and the calcium and magnesium additive is dissolved first and then slowly dripped into the water body. When dripping, the dripping position should be placed above the submersible pump or gas stone to play a stirring role so that the additive is evenly distributed in the water.
Fourth, the stability of pH
The pH of the cultured water body of rice shrimp is 6 to 7, which is a weak acidic water quality. In the process of rice shrimp farming, pH is not static, starting from landscaping, different substrates, landscaping materials, various drugs and additives, and then to the breeding of rice shrimp, feed feeding, biological metabolism, etc. will change the pH of the water body. Measurement records are therefore required on a regular basis. For amateurs, I recommend using cheap and practical pH test strips, while professional farmers can buy accurate pH meters. These data can provide a reference for pH changes during water change and filter media replacement, and even provide a basis for the diagnosis of certain diseases, making production more efficient, stable and safe. For how to stabilize the pH, the author controls it through different substrates, and the use of ADA sediment can make the water body weakly acidic, and the use of river sand, gravel, etc. can make the water body weakly alkaline. ADA sediment is rich in organic components and nitrogen, which can make the water less acidic. However, with prolonged use, this function will weaken, so it is necessary to replace it regularly; acid-base buffers can also be used, but the author does not recommend using them, and can only be used as a last resort, because acid-base buffers will bring in unnecessary ions and form other salts.
Fifth, the management of nitrogen-containing metabolites
In water quality management projects, ammonia nitrogen, nitrite and nitrate are important components of nitrogen-containing metabolites and are also mandatory indicators for shrimp farming. These metabolites contribute to the growth of plants, but exceeding a certain concentration can endanger the health of rice shrimp. Therefore, how to control the concentration of metabolites has always been a problem that plagues the majority of enthusiasts. At present, a lot of scientific research efforts have been invested in other farmed species, but the effect is still not in the ideal state. The author believes that since there is no shortcut to go, let's take the old way. We may wish to start from the microorganism, water body and filter media and filter bed, with the number of water changes, feeding volume and feeding times for comprehensive management. The specific measures are as follows: (1) Microorganisms can be cultivated in the water body or filtered parts, such as nitrifying bacteria, denitrifying bacteria, photosynthetic bacteria and other beneficial bacteria, which can reduce the level of nitrogen-containing metabolites and the accumulation rate of the water body. (2) Increase the total water turnover by appropriately reducing the amount of water change and increasing the number of water changes, and reduce the level of nitrogen-containing metabolites. (3) Feeding a small amount of food can not only reduce the waste of bait, but also avoid the pollution caused by the fermentation of residual bait to the water body. The biomass of the water body determines the basal metabolic amount, which is affected by the feeding temperature, feeding amount and number of feedings. Therefore, whether it is indoor and outdoor aquaculture, as well as aquarium, plastic barrel, cement pond or earthen pond culture, it is necessary to circulate filtration systems and cultivate specific microorganisms to metabolize and transform them.
Sixth, the control of microorganisms
In the past, most of the water quality monitoring focused on physical and chemical parameters, and few microbes in the water body or substrate were understood. But for rice shrimp, microbes tend to affect the growth, survival, body color and reproduction rate of the entire population. According to the degree of influence on rice shrimp, it can be divided into beneficial species, the former including beneficial bacteria, green algae that can be eaten by rice shrimp, etc., and the latter contain pathogenic bacteria, cyanobacteria that can secrete toxins, hydra and planarians that will prey on juvenile shrimp. If the above harmful species appear, the author recommends: (1) suck the bottom every 3 days, mainly clean the residual bait to keep the aquarium clean. At the same time, be careful not to suck the baby shrimp away. (2) Planting an appropriate amount of aquatic grass, in addition to aesthetics, plants can absorb ammonia nitrogen and produce oxygen, which has a certain inhibitory effect on anaerobic bacteria. (3) Water change can reduce the density of harmful species, reduce the probability of disease, every three days, the amount of water exchange is 1/3. (4) Pests such as hydras can be disinfected for 24 hours with 200 mg/l of formaldehyde. However, it is necessary to change 1/2 of the water for two consecutive days to eliminate formaldehyde. It is also possible to disinfect regularly once a month.
