Common diseases of koi and methods to improve the cure rate of fish diseases

I. Observe frequently, treat early

Generally, afterkoifishare infected or invaded by pathogens, there is a process with some signs, such as sick fish moving sluggishly, often swimming slowly at the water surface, not schooling together; if startled, they sink slightly and then immediately rise to the surface. Some fish, when the disease first strikes, swim frantically and dart about, or their body color turns dull gray and scales fall off. For another example, after an outbreak of hemorrhage disease in white crucian carp, wild small miscellaneous fish in the pond die in the early stage.

II. Correct diagnosis, suit the remedy to the case

First, based on climatic characteristics, water source conditions, source of fish fry, polyculture ratio and density, feeding management, the pattern of fish disease outbreaks over the years, and the condition of the fish school's appetite, behavior and body color, conduct on-site investigation and analysis. Then take dying sick fish or dead fish carcasses that have not yet decomposed, and carry out naked-eye examination or microscopic examination of the body surface, gill filaments, muscles, internal organs and other parts. Check whether the body surface shows large parasites such as Chinese copepods (Sinergasilus) and anchor worms (Lernaea), or bleeding spots and patches, fallen scales, rotten fins, ** redness and swelling, and similar phenomena. For the gills, check for congestion and erosion of the gill cover, the color of the gill filaments, the amount of mucus, parasite infestation, and rotten gill filaments carrying mud. After cutting open the abdominal cavity, check whether there is ascites, intestinal inflammation, congestion, and congestion of organs such as the liver and spleen. Peel back the skin to see whether the muscles bleed, and so on. Based on the specific symptoms found, first diagnose parasitic, bacterial, viral diseases or complications, then conduct a comprehensive analysis based on the performance of the sick fish, make a correct diagnosis, and suit the remedy to the case.

III. Measure accurately, use the correct dosage

Accurate measurement and correct dosage are another key to whether fish disease treatment works well. For external-use drugs, when splashing over the whole pond, the pond water volume must be calculated accurately, and the influence of water quality characteristics and the water temperature at the time should be taken into account; for example, when there is much organic matter, the water is relatively fertile, and the water temperature is low, the dosage should be somewhat higher. The calculation of pond water volume should be based on the actual water surface area and average water depth. The average water depth should be calculated based on the average of several depths at different points in the pond. The dosage of oral drugs is expressed as how much drug is ingested per kilogram of fish body weight, and there are usually two calculation methods:

Calculation by weight and calculation by feeding rate should be used flexibly. When most fish in the pond have a strong appetite, calculating by the total weight of the pond fish is more accurate; when the pond fish are seriously ill or the weather is bad, causing reduced appetite, the drug should be mixed into the bait at a relatively higher ratio according to the estimated feeding rate, to ensure that sick fish that can still eat get enough of the drug. When preparing medicated bait, the loss of the drug in water should also be taken into account. Pay attention to estimating the total number and weight of the pond fish, and take into account the growth and weight-gain ratio at each stage; the feeding amount of medicated bait must not be calculated based on the fish fry stocked.

IV. Master the characteristics of drugs, use drugs scientifically

　　koiCommon drugs for fish diseases each have their own physicochemical characteristics, and their storage and use should be rationalized to avoid failure due to improper storage or use. For example, which drugs can only be used externally, which drugs have good oral effects, and which drugs cannot be used together. Which drugs work better when used together, and which drugs are affected by environmental factors, and so on. Medicated bait should take into account the fish's living habits, and be made into different baits such as floating, sinking and micro-particle types. Generally, when black carp, common carp and crucian carp are affected, sinking medicated bait should be fed; when grass carp are affected, feeding floating medicated bait or mixing the drug onto aquatic plants is better; when silver carp are affected, micro-particle medicated bait should be fed, and a certain amount of binder must be mixed in during preparation to prevent the drug from dispersing in the water. For drug splashing, the drug must be fully dissolved and then evenly splashed over the whole pond; the splashing time is better in the afternoon, because the water temperature is higher in the afternoon and the drug efficacy is higher. When splashing drugs, splash gradually from the upwind area to the downwind area; after splashing, the remaining residue and undissolved drug must not be splashed into the pond. Otherwise, if fish swallow it, it will cause poisoning and death.

V. According to the type of disease, use a full course of treatment

The course of treatment is the fundamental guarantee for curing fish diseases; without a sufficient course of treatment, the pathogens cannot be completely eliminated, and the drug will not achieve its effect. Therefore, using a full course of treatment is an important link in completely eliminating pathogens and consolidating the treatment effect. In practice, the length of the course of treatment should be based on the specific category of the disease the fish has. For invasive diseases, which are caused by parasitic infestation, generally using insecticidal drugs for 1 to 2 days as one course of treatment can achieve the therapeutic purpose; for bacterial and viral diseases, generally 3 to 5 days is one course of treatment. As for how many courses to use, this should be determined by the severity of the condition and the urgency of the disease course. For diseases that are severe and last a long time, two to three courses of treatment must be used; otherwise, the curative effect will not be thorough, and there is a possibility of recurrent infection.

VI. Several points to note

1. Before feeding medicated bait, feeding should be stopped for 1 day, so that the fish are in a hungry state, and after the medicated bait is fed, they can finish eating it quickly.

2. During treatment and just after recovery, large water changes and netting should not be carried out, so as not to irritate the fish, cause stress reactions, and worsen the condition or cause relapse.

3. Treatment of fish diseases should adopt a combination of oral medication and external disinfection; relying solely on oral drugs cannot achieve the effect of attacking from both inside and outside.

4. When treating koi diseases, the same drug must not be used alone many times, so as not to cause pathogens to develop resistance to that drug; drugs should be used alternately.

5. Once a disease breaks out, no matter whether the treatment effect is good or bad, losses cannot be avoided. Therefore, the prevention and control policy of "prevention first, treatment as a supplement" must be adhered to at ordinary times.