China Aquatic Products Channel reported that it has recently seen many reports of violent ponds in crab ponds, either because of high temperature and lack of oxygen or because of serious decay of aquatic grasses, or because of improper killing of cyanobacteria... After these situations, many ponds also use sodium thiosulfate to deal with these problems urgently, but there are many pond treatment effects are not ideal, and even the situation of the storm pond, and most crab farmers blame the use of sodium thiosulfate, because sodium thiosulfate consumes oxygen, which leads to the occurrence of the storm pond situation, so many crab farmers pile dead crabs to the door of the animal protection store, which seriously affects the normal operation of the animal protection store, and even extreme crab farmers drink pesticides at the entrance of the animal protection store. In this way, we will force Baomen City to compensate the dead crabs. Leaving aside who is right and who is wrong, but the author has also used sodium thiosulfate many times to deal with the problems encountered in pond aquaculture: crabs are grassed in the middle of the night during high temperatures, pond ammonia nitrogen is seriously exceeded, fish floating in the middle of the night, water redness after pouring algae, etc., have achieved good results, but there has not been a situation of storm ponds, here to share a personal understanding of sodium thiosulfate, for reference only.
Sodium thiosulfate, also known as sodium hyposulfite, soda, and hyperbo. It is a common thiosulfate, a colorless, transparent monoclinic crystal. Density 1.729g/cm3, melting point 40 ~ 45 °C, sodium thiosulfate is easily soluble in water, soluble in water after heat absorption (cooling and bottom heat), aqueous solution is weak alkaline, easily soluble in ammonia, insoluble in alcohol.
At 48 °C, it is transformed into the dihydrate compound na2s2o3?2h2o, and five crystalline waters are lost at 100 °C. It is easy to weather in dry air above 33 °C, easy to deliquebilize in humid air, and is oxidized (oxygen-consuming) and carbon dioxide carbonated by oxygen in the air.
a. Sodium thiosulfate is stable under alkaline or neutral conditions, decomposes in case of acid, and the disproportionation reaction immediately liberates sulfur dioxide gas and produces the precipitation of sulfur (with weak disinfection effect), showing redox properties. Sulfur atoms are unstable and become sulfur ions through the action of bacteria, which can form a non-toxic precipitate with heavy metal ions (remove heavy metal toxins).
b. Heated in air is oxidized and decomposed into sodium sulfate and sulfur dioxide. Burning in isolated air produces sodium sulfate, sodium sulfide and sulfur.
c. Sodium thiosulfate has a strong complexing ability (to solve the black water and red water caused by inverted algae), and can form complexes with silver bromide. According to this property, it can be used as a fixer.
agbr+2na2s2o3=nabr+ag3[ag(s2o3)2]
d. Sodium thiosulfate has a certain reducibility, which can reduce chlorine and other substances (except for residual chlorine), and its reductivity can also degrade the toxicity of organophosphorus insecticides.
s2o32-+4cl2+5h2o=2so42-+8cl-+10h+
a. Cool down and remove the bottom heat. Mainly in July and August when the high temperature, due to the continuous high temperature, resulting in pond water heating, when the bottom water of the pond is hot, crabs will appear on the grass situation, mainly in the first half of the night, this time the use of sodium thiosulfate can be solved, the first half of the night crab grass on the serious need to use for two consecutive days, generally in the evening direct dry sprinkling. Granular oxygen is required for use.
b. Remove residual chlorine from water. Mainly used after Qingtang, some places Qingtang will use bleach powder (the main ingredient calcium hypochlorite, calcium chloride), the use of bleach powder after three or four days of sodium thiosulfate, can react with calcium hypochlorite with strong oxidation, the formation of harmless chloride ions.
c. Detoxify organophosphorus insecticides. Organophosphorus insecticides are commonly used in aquatic products are octylthion and dimethoate, octyl thiophos is mainly used in fish ponds, diophthion is mainly crab pond, insecticide use, after use can use sodium thiosulfate detoxification.
d. Remove the toxins of heavy metal ions. Heavy metals are not used much in crab ponds, mainly aluminum and iron ions have been used as flocculants to purify water quality. Common fish ponds are mainly copper sulfate and ferrous sulfate used for insecticide. Sulfur ions can react with heavy metal ions to form a non-toxic precipitate and relieve the toxicity of heavy metal ions.
e. Reduction of pond ammonia nitrogen. The specific principle of sodium thiosulfate to reduce ammonia nitrogen is not very clear, but in practical applications, the effect of sodium thiosulfate to rapidly reduce ammonia nitrogen is still relatively good, and the specific case can be Baidu "Silver carp poisoning death in the pond of ammonia nitrogen 4.5, is there any salvation?" 》
f. Control black water and red water caused by inverted algae. After pouring algae, the water is black and red, the main reason is that the algae that dies after pouring algae is decomposed into various macromolecules and small molecules of organic matter, making the water quality look black or red, sodium thiosulfate has a complexation, can be complexed with these large molecules, small molecules of organic matter, so as to achieve the effect of black water, red water.
g. Release sulfur atoms, has a certain disinfection effect. Sodium thiosulfate is basically not used as a disinfectant, mainly because the sulfur atom is unstable, the disinfection effect lasts short, and the disinfection effect is relatively weak.
When used with granular oxygen, although some granular oxygen and sodium thiosulfate will be lost, the safety will be greatly improved.
c. Because the floating head caused by excessive ammonia nitrogen can be used, it is necessary to use granular oxygen before use.
d. Sodium thiosulfate is used in seawater, and the water may become turbid or black, which is a normal phenomenon.
In the treatment of the above several cases, more or less will use sodium thiosulfate, but because of the use of sodium thiosulfate and lead to crab moat is unlikely, on the one hand, the product labels of each manufacturer will have a guide dosage, this dosage is after thousands of times of use to determine the final guidance dosage, according to the instructions to use is generally not a problem; on the other hand, the current market of animal protection products are mixed, The sodium thiosulfate we purchase does not guarantee that the active ingredient will reach the active content indicated on the label 100%, so even if it is used according to the maximum dosage indicated, it will generally not be a problem.
(1) When crabs begin to die in small quantities, a large number of crab deaths occur with sodium perthiosulfate. This situation is mainly because the crab has reached the stage of the storm pond, with or without sodium thiosulfate will immediately appear a large number of crab deaths, but the timing of using sodium thiosulfate is not good, just encountered the stage where crabs began to die in large quantities, giving people the illusion that it is because of the use of sodium thiosulfate and lead to a large number of crab deaths.
(2) In the case of continuous high temperature, inverted algae, Elek algae rot, crabs do not appear to die, in order to reduce the water temperature, treatment of black water or red water, sodium thiosulfate is used, but after the use of sodium thiosulfate crabs have a large number of deaths, the main reason may be the use of sodium thiosulfate, the pond dissolved oxygen itself is relatively low, has been at the critical point of crab pond, and sodium thiosulfate after use will cause dissolved oxygen reduction, at the critical point of crab pond, Sodium thiosulfate may be the last straw to crush crabs.
Medicine and poison, the essential difference is in the amount of use, sodium thiosulfate, used well, is a good medicine, treatment of water quality problems can play an immediate effect; but not good, may be a dose of poison, so that the entire pond crab army destroyed, heavy losses. How to use sodium thiosulfate well, but also need to further explore and summarize in practice, I hope it can be used just right!