Water is the decisive factor for shrimp to grow and develop, bringing more value to farmers. Because farmers often say that: “Shrimp farming is raising water”. Therefore, the source of shrimp farming water must be clean and unpolluted. So how can we assess the quality of pond water as well as the ability to influence some important factors in the process of water quality management? ? It depends on the hydrological and physicochemical factors. Therefore, farmers need to pay attention to them to limit the risks in aquaculture.
1. Hydrological factors
This is a factor having a strong impact on their health. When the temperature changes rapidly, it is easy for them to suffer from heat shock and weaken. In addition, this is also a factor that causes their disease. When high temperatures lead to mass mortality, causing heavy losses for farmers. Not only that, but the high temperature also causes them to change their body temperature according to the environment, leading to an ongoing metabolic process that makes them eat more. However, the amount of yeast in their body is limited and difficult to absorb as well as increases the cost of farmers, but the low efficiency
Therefore, the ideal temperature for shrimp survival and reproduction should range from 20-30 C.
b) Clarity, turbidity water
One of the equally significant factors that controlled need is turbidity and clarity. Because it affects the shrimp’s growth and farmers are difficult to recognize. Turbidity, clarity depends greatly on suspended silt or microbial population (algae, bacteria). Because algae are not only a food source but also a source of oxygen consumption as well as a factor to determine the turbidity of shrimp culture water. Thereby, helping farmers determine the nutrient level in the water when observing the pond water because too clear water reflects poor nutrition, and vice versa, if the water is too cloudy, it will lead to eutrophication, which causes oxygen deficiency. That is why it should be to balance the algae in the lake. And the suitable clarity for shrimp farming water is 30 – 35 cm.
2. Physicochemical factor
pH is an important indicator causing their health greatly and fluctuates based on factors: weather, light, temperature, algae… Therefore, farmers need to be careful before changing pH to avoid damage during culture. If the pH is high, it will increase NH3 in the water and vice versa, in contrast, it will produce H2S gas in the pond water. These are two extremely dangerous gases that cause shrimp death. In addition, the change of pH can also cause the molting process and harden the shrimp shell. Besides, their growth is slow as well as reduces the immune system susceptibility to pathogens in the pond.
Therefore, the pH should range from 7.5 to 8.5, and the daily variation should not be more than 0.5.
b) Solubility (DO)
Oxygen helps maintain life and dissolved oxygen is the necessary oxygen for the respiration and development of aquatic organisms, not only shrimp. Although at each stage, their DO needs are not the same because it depends on factors: the health, absorption capacity of each individual… However, farmers should still pay attention to this indicator. Because, if the amount of DO is less than 5 mg/l, it will lead to the phenomenon of eating less in shrimp, slow growth, affecting the molting process. If the situation is prolonged, shrimp will be susceptible to other dangerous diseases as well as shrimp death
c) Nutritional salt
Supporting salts KCl, MgCl2, MgSO4… appropriately to help aquatic species in general and shrimp in particular, develop in the best way to bring high profit from farming. Because, the salinity of salt affects the survival, development, and maintenance of physiological functions of shrimp through the process of regulating osmotic pressure as well as increasing the antibacterial ability and immunity in shrimp. However, it is necessary to control the salinity strictly. Because of:
If the salinity is too low, the icons Ca2+, Mg 2+, Na+… in the water with low content make the molting process of shrimp uneven. Their shell becomes soft after molting, increasing the loss rate many times leading to reduced shrimp resistance function.
In contrast, if living in an environment with high salinity, above the tolerance level, shrimp will be stunted, slow to grow, even shocked, and die in mass. Moreover, the salinity is high causing white feces disease and acute hepatopancreatic necrosis. It will develop very complicatedly, causing epidemics causing great economic losses.