Fish Feed Machine Knowleagde

The pH value of the water body refers to the negative value of the common logarithm of the hydrogen ion concentration in the aquaculture water body, that is, pH=-lg[H+]. In the process of aquaculture water quality management, pH management is an important part of water quality management. In the entire breeding cycle, an appropriate pH value is not only a necessary condition for the survival of the aquaculture object, but also an important reflection of the stability of the entire pond water quality. index. In aquaculture water bodies, the most suitable pH range for most fish and shrimp is neutral to slightly alkaline (ie 7.0-8.5), and pH<4.4 or pH>10 can directly lead to the death of aquatic animals. Generally, in aquaculture water, pH<6.5 or pH>9.0 indicates that the pH is beyond the suitable range for fish and shrimp to survive, and corresponding measures need to be taken to adjust.

The hazards of excessive pH are mainly manifested in the following aspects:
1. Excessive pH will corrode the gills of fish, causing respiratory disorders in fishes, and long-term tissue lesions in the gills.
2. The pH of the water is too high, and the proportion of ammonia nitrogen in the water in the form of molecular ammonia increases greatly. When the pH exceeds 9.0, the content of molecular ammonia is greater than 35% (when the water temperature is greater than 25 degrees), which greatly increases the toxicity of ammonia nitrogen, and finally Affect the growth of farmed animals.

The control measures mainly include the following aspects
1. Change the water. For ponds with sufficient water sources and good water quality, the pH of the aquaculture water can be lowered by changing the water.
2. To control algae activities, you can choose copper sulfate and other algae killing drugs to kill some algae or use polyaluminum chloride and other flocculants to precipitate algae, reduce the abundance of algae in the pond to reduce the consumption of CO2 by photosynthesis, thereby controlling the pH Elevated.
3. Use microbial preparations to accelerate the decomposition of organic matter. The CO2 generated by the decomposition of organic matter provides more CO2 sources, eases the positive movement of the CO2 balance system, reduces the production of OH-, and uses certain probiotic species and algae at the same time Competitive relationship in nutrition to inhibit algae activity, reduce the consumption of CO2, and lower pH. In actual operation, EM bacteria can be used together with brown sugar and other nutrients to promote the growth and reproduction of beneficial bacteria to accelerate the decomposition of organic matter in water.
4. Use chemical methods to neutralize the OH- in the water body, mainly acetic acid (acetin) and citric acid, which are dissolved and spilled on the breeding water body, and the acid is used to directly neutralize the OH- in the water body to reduce the pH of the water body. This method It is mostly used when the pH of the water body is too high and urgent treatment is needed.

Harm of too low pH in aquaculture ponds and control measures
1. The hazards of low pH mainly include the following aspects:
On the one hand, a too low pH can directly affect the physiological activities of the fish, reduce the pH value of the blood of the breeding object, weaken the oxygen-carrying capacity in the period, and cause the fish to be physiologically hypoxic. The metabolism and growth of the breeding objects are inhibited.
In a low pH water environment, the content of molecular hydrogen sulfide in the water greatly increases. When the pH value is lower than 6.5, more than 70% of the hydrogen sulfide in the water exists in non-ionic form, which increases the toxicity of sulfide.
Since the most suitable pH for most aerobic bacteria is neutral and slightly alkaline, a too low pH will inhibit the decomposition of bacteria and slow down the decomposition of organic matter in the water. At the same time, a too low pH is not conducive to the nitrification reaction. , Resulting in the accumulation of ammonia nitrogen and nitrite, which are decomposition products of organic matter, and affect water quality.
2. Adjustment measures
For aquaculture water with a pH lower than 6.5, it is usually possible to increase the pH of the water by splashing quicklime with water. However, in seawater, there are too many calcium and magnesium ions in the water, due to the combination of magnesium ions and hydroxide ions. Combined with precipitation, it is much more difficult to increase the pH by splashing quicklime with water than with fresh water.
In fishery production, quicklime or adding acid is most commonly used to adjust the pH value of the water body. When the pH value of the aquaculture water body is low, use quicklime to increase the pH value; According to theoretical calculations, the amount of quicklime and concentrated hydrochloric acid required to adjust the pH of pure water with a depth of 1 meter per mu.
The main component of quicklime is calcium oxide (CaO), which is dissolved in water and the reaction equation of water is CaO+H2O=Ca(OH)2, and the ionization equation of Ca(OH)2 in water is Ca(OH)2 = Ca2+ + 2OH-. To increase the pure water with a pH of 7 to 8, the concentration of OH- in the water should be increased from 10-7mol/L to 10-6mol/L, that is, the concentration of OH- should be increased by 10-6-10-7 = 0.9×10-6 mol/L, the concentration of Ca2+ is one-half of the concentration of OH-, so the concentration of CaO needs to be 0.45×10-6 mol/L, and the molecular weight of CaO is 56, so the mass of CaO that needs to be added is 0.45×10-6×56=2.52×10-5g/L, the amount required to convert to 1 acre of water (667m3) with a water depth of 1 meter is 2.52×10-5×667m3×1000=16.78 g. According to the theoretical calculation of this method, the amount of quicklime needed to increase the pH value of pure water with a depth of 1 meter per acre.

The solubility of Ca(OH)2 at 20℃ is 0.166g/100g, and the pH value of its saturated solution is 12.65. The pH value in the table is below 12.65, so the Ca(OH)2 generated by adding CaO can be dissolved and can be completely ionization.
From this theoretical calculation table, we can get the following revelation (taking the addition of quicklime to increase the pH value, for example, adding acid to reduce the pH value is the same):
1. When the pH value rises by one unit, the amount of quicklime is not the same. For each unit of pH increase, the amount of quicklime required is not the same. For example, if the pH value rises from 5 to 6, 0.2g/667m3 of quicklime is needed, and when the pH value rises from 6 to 7, 1.7g of quicklime is needed, from 7 liters. To 8, 16.8 grams of quicklime is needed, and from 10 to 11, 16783.2 grams of quicklime is needed. Some data say that for every gram of quicklime added to a certain volume of water, the pH value will rise by one unit, which is not accurate. An experimental study on adding alkali to adjust the pH value in a water plant proved this point by adding lime to the raw water of a water plant to adjust the pH value. The pH value of the raw water was 6.86, and 1 mg of quicklime was added to it, and the pH value was increased to 7.26 , The pH value increased by 0.4, and when 7mg quicklime was added to the raw water, the pH value was 9.09, and then 1mg quicklime was added, the pH value rose to 9.20, and the pH value only increased by 0.11.
2. The lower the pH value that needs to be adjusted, the less quicklime is needed; the higher the pH value that needs to be adjusted, the more quicklime is needed. For example, when the pH value is raised from 5 to 6, only 0.2g/667m3 of quicklime is needed, and when it is raised from 6 to 7, only 1.7g/667m3 is needed. However, when the pH is raised from 10 to 11, 16783.2g/667m3 of quicklime is needed.
3. From different pH values ​​to the same pH value, there is little difference in the amount of quicklime required. For example, if the pH value is raised from 5 to 8, it needs 18.6 g/667m3 of quicklime, from 6 to 8, it needs 18.5 g/667m3 of quicklime, and it needs 16.8 g/667m3 of quicklime if it rises from 7 to 8, and it needs 16.8 g/667m3 from the same pH value. For example, if the pH value is raised from 5 to 6, 0.2 g/667m3 of quicklime is needed, and from 5 to 7, 1.8 g/667m3 of quicklime is needed, and from 5 to 8, it needs Quicklime is 18.6 g/667m3, rising from 5 to 11, but 18648.0 g/667m3 of quicklime is needed.
4. The same amount of quicklime has different effects on different basic pH values ​​to increase the pH. That is, the same amount of quicklime has a more obvious effect on changing the pH value for water bodies with a lower pH value than that of water bodies with a lower pH value. For example, 0.2g of quicklime can increase the pH value of 666 m3 pure water with a pH of 5 to 6, and the pH value increases by 1 unit, while 666 m3 of pure water with a pH of 10 plus 0.2g of quicklime 0.2g Quicklime cannot be increased by 1 unit, but 16783.2g of quicklime is required to increase by 1 unit.
5. In practice, there are factors that consume hydroxide ions in the sediments at the bottom of the water and ponds, such as HCO3-, Fe2+, Fe3+, Mg2+, free CO2, etc., which can be combined with hydroxide ions. The quicklime required for the pH value of the water body is much higher than the theoretical calculation value. However, in the actual use of quicklime, we found that some farmers use 60-75kg/mu of quicklime when clearing their ponds, some use 100 kg/mu, and some use 125-150 kg/mu. In fact, as long as the pH of the water reaches 11, it can have the effect of sterilizing and killing wild fish. From theoretical calculations, it can be known that whether the original pH value of pure water with a depth of 1 meter per mu is raised from 5 to 11, or from 10 to 11, only about 18 kg of quicklime is needed. Therefore, farmers do not need to blindly ask for more when using quicklime to clear the pond, as long as the pH value can reach 11, so as to avoid waste.

For ponds where the water source is convenient and the pH of the source water is appropriate, it can also be solved by changing the water.
Dredging the silt in the breeding gap to remove the excessive organic matter at the bottom of the pond to avoid the formation of anaerobic decomposition and acidification of the organic matter at the pond bottom.
Properly cultivate algae, promote the reproduction of beneficial algae, promote the positive movement of the CO2 balance system through the use of carbon dioxide by algae photosynthesis, and increase the OH- concentration in the water to increase the pH of the water.