What are the commonly used drugs for fish? A detailed introduction

At present, there are many kinds of @#@233@#@ commonly used drugs on the market. Because fish drug production is not yet standardized, some products from various manufacturers do not indicate their active ingredients, and the trade names of some similar finished drugs are not consistent with their corresponding chemical names. This is not conducive to our understanding of the active ingredients of drugs and also creates certain difficulties for scientific and rational medication. In order to popularize fish disease prevention and treatment technology, we will successively introduce knowledge about drugs commonly used in fish farming. This is expected to improve our understanding and awareness of commonly used drugs so that drugs can be used scientifically and rationally in production.

I. Disinfection and sterilization drugs

There are many kinds of disinfectant and antiseptic drugs commonly used for the prevention and treatment of bacterial fish diseases in pond fish farming, most of which are chlorine-containing compounds. Among them, the more commonly used ones are mainly bleaching powder, bleaching concentrate, dichloroisocyanuric acid, trichloroisocyanuric acid, and chlorine dioxide, etc.

(I) Bleaching powder

[Properties] Bleaching powder is a mixture of calcium hypochlorite, calcium hydroxide, and calcium chloride. The finished product is a grayish-white powder with a chlorine odor. Its aqueous solution appears turbid, with a large amount of suspended sediment; bleaching powder has very poor stability. When exposed to air, it can absorb moisture, decompose slowly, and undergo a chemical reaction with carbon dioxide in the air. It generates calcium chloride, which has no sterilizing effect, and thus becomes ineffective. Storage time is generally three to six months. Storage conditions should be sealed and placed in a cool, dry place. In summer, when air humidity is high, the storage period is relatively shortened. Generally, it is advisable to purchase one with a relatively short time since production. The available chlorine content should not be less than 25%. The available chlorine of bleaching powder can be determined by the following simple method.

1. Material preparation

(1) One bottle of blue-black ink. Generally, blue-black ink such as Beijing brand or Hero brand can be used. As long as it has not been diluted with water and has no precipitate, it can be used;

(2) One 1 mL pipette. It can also be replaced by a 1-2 mL syringe; any syringe with 0.1 mL graduations can be used;

(3) One small white porcelain bowl;

(4) One glass rod, which can also be replaced by a water-nonabsorbent plastic rod;

(5) One 100 mL graduated cylinder, which can also be replaced by a graduated medicine bottle or an infusion saline bottle;

(6) One ordinary small balance, which can also be replaced by a relatively high-precision small hand scale.

2. Determination method

(1) When taking bleaching powder samples for available chlorine determination, random sampling should be adopted. Generally, roughly equal amounts (about several tens of grams) of bleaching powder can be randomly taken from different parts (upper, middle, and lower layers) of three to five containers, and then mixed evenly as the sample to be tested.

(2) Weigh 5 grams of bleaching powder sample, place it in a graduated cylinder, add a small amount of boiled and then cooled drinking water (the water is required not to contain dissolved carbon dioxide), stir and grind the bleaching powder and water with a glass rod, then dilute to 100 mL. After fully stirring, let it stand;

(3) After the solution becomes clear, use a pipette or syringe to draw a certain amount of the upper clear liquid and drip it drop by drop into the white porcelain bowl for a total of 38 drops (no more and no fewer drops);

(4) Wash the used pipette or syringe and shake it dry; draw a small amount of blue ink and rinse the tube wall with the blue ink, then discard it, draw blue ink again, and titrate it into the bleaching powder clear liquid in the porcelain bowl. While dripping, stir with a clean glass rod. The color of the bleaching powder clear liquid changes from brown to yellow, and when it finally appears stable blue-green, that is the endpoint of titration.

(5) The number of drops of blue ink used is the percentage of available chlorine in the bleaching powder (for example: if 24 drops of blue ink are used, then the available chlorine of the bleaching powder is 24%).

[Action] When bleaching powder is added to water, it generates hypochlorous acid and basic calcium chloride. Hypochlorous acid is unstable and immediately decomposes to release active chlorine and atomic oxygen, showing a sterilizing effect. Among active chlorine, the sterilizing power of hypochlorite ions is weak. Its mechanism of action is chlorination and oxidation as well as the ability to inhibit the activity of certain sulfhydryl-containing enzymes in bacteria, thereby hindering bacterial growth and reproduction. Its sterilizing effect is strong, but not lasting. Its sterilizing use is enhanced in an acidic environment and weakened in an alkaline environment.

[Use] Bleaching powder is one of the commonly used drugs in fish disease prevention and treatment. It is mainly used to prevent and treat bacterial fish diseases and to kill bacteria on the outside of fish and in water bodies.

[Usage and dosage]

1. Pond clearing and disinfection: dry method, 10-20 kg per mu; pond clearing with water, 25-35 kg per mu of water surface (water depth 1 m).

2. Whole-pond splashing: make the pond water concentration 1 ppm (containing 1 mg per liter of water). It can be used to prevent and treat bacterial fish diseases such as gill rot disease, red skin disease, and white head and white mouth disease.

3. Fry disinfection: medicated bath, soaking in 10-20 ppm aqueous solution for 10-30 minutes, can kill bacteria on the body surface and gills of aquatic animals.

4. Feed disinfection: soak aquatic plants in 6-10 ppm bleaching powder aqueous solution for 20-30 minutes; disinfect Artemia cysts by soaking in 300 ppm aqueous solution, then rinse until there is no chlorine odor.

5. Tool disinfection: soak and disinfect in 5% bleaching powder aqueous solution.

6. Feeding ground disinfection: regularly splash bleaching powder at the feeding ground. The dosage depends on the size of the feeding ground, water depth, and water temperature, generally 250-500 grams. Splash the drug first, then feed the fish. A hanging basket method can also be used at the feeding ground (waste mineral water bottles can be perforated to replace bamboo baskets) for fish disease prevention and treatment.