How to prevent and treat common koi diseases? A full breakdown of practical techniques

Many people choose koi as the fish species when keeping feng shui fish, because koi are fish with a story, and besides, this fish is one of our country's ancient fish species, so basically when keeping feng shui fish, people choose koi. But feng shui fish generally must not be kept to death, and if one does die it must be replaced immediately to make up the number. Below let's take a look at the prevention and treatment techniques for common koi diseases!

Carp pox disease

[Cause] Appears in late autumn and winter when water temperature is relatively low (around 15°C)

[Symptoms] In the early stage of the disease, small milky-white spots appear on the body surface or tail fin, covered with a very thin layer of white mucus, and later gradually expand until they spread over the whole body. The skin surface at the lesion thickens and forms large, paraffin-like growths. Once these growths reach a certain size and thickness, they fall off on their own, and in the water they spoil the water quality, while new growths grow again at the site where they fell off. Diseased fish infected with carp pox gradually become thin, swim sluggishly, have a poorer appetite, often sink to the bottom, and die one after another.

[Treatment] ① Long-term medicated bath in 0.1-0.3 mg/kg chloramphenicol solution. ② Inject chloramphenicol into the fish body, with a dosage of 25 mg per fish.

[Prevention] ① Add fresh water to the pond, remove shed material from the pond bottom at any time, and improve water quality. ② Strengthen autumn rearing work, enhance nutrition, so that koi have a certain degree of fatness before winter and stronger resistance to low temperature and disease. ③ Sprinkle nitrofurazone at 1-2 mg/kg over the whole pond to prevent the occurrence of carp pox.

Saprolegniasis (fungus disease)

[Symptoms] A layer of “white hair” grows on the fish body. If not treated in time, when the pathogen invades the body, the fish will gradually weaken and die. When it parasitizes the gills, it forms gill fungus disease, which often causes explosive deaths. Saprolegniasis is caused by a filamentous fungus and mostly occurs in ponds with a large number of fish or in turbid, stagnant water. Fish that are thin and weak or have external injuries are more easily infected. Large amounts of cotton-like mycelium grow at the lesion, hence it is also called white hair disease.

[Cause] The main reasons koi suffer from saprolegniasis are careless handling during capture and transport causing skin abrasions, or parasites damaging the gills and body surface, or skin frostbite due to water temperature being too low, so that water mold spores invade the wound and cause infection. When the water temperature is suitable (around 15-25°C), dense mycelium grows in 3-5 days, and when the number of infections is large it can lead to the death of diseased fish. Water mold exists all year round, and late autumn and early spring are the epidemic seasons. It can infect everything from fish eggs to fish of all ages. When the incubation water temperature is low, water mold disease is very likely to occur on fish eggs.

[Treatment] ① Wash with 1.5%-2.5% salt water, remove the hair-like material, then apply 2% merbromin, and then give a bath with fish terramycin. ② Apply a 0.1%-1% concentration malachite green aqueous solution to the wound and the places where water mold is attached. ③ Soak the fish body in a 1:15000 malachite green aqueous solution for 3-5 minutes. ④ Soak the fish body in a 10 mg/kg potassium permanganate aqueous solution for half an hour.

[Prevention] ① When netting, catching, transporting and stocking fish, handle them carefully so as not to injure the fish body. ② Soak fish eggs in a 1:15000 concentration malachite green aqueous solution for 10-15 minutes, once a day for 3 consecutive days, to prevent water mold disease in fish eggs. ③ For injured brood fish, apply gentian violet or potassium permanganate to the wound to prevent water mold infection. ④ For each hectare of pond, mix 75 kg sweet flag, 7.5-15 kg salt and 225-300 kg human urine, then sprinkle over the whole pond once a month.

Skin inflammation and congestion disease

[Cause] Those affected are mostly large individuals of the current year and koi over one year old. Late spring to early autumn is the epidemic season, and it can cause massive fish deaths. It is most likely to be epidemic when the water temperature is 20-30°C, and below 20°C a few diseased fish still appear and continue to die. This temperature range is also the peak season for fish growth, so the harm is great. When the temperature drops to around 10°C this fish disease no longer occurs, and this pattern can be used to carry out temperature-controlled treatment of diseased fish.

[Symptoms] The skin becomes inflamed and congested, most commonly around the eye sockets, gill covers, abdomen, caudal peduncle, etc. Sometimes there is also congestion at the base of the fin rays, and in severe cases the fin rays rupture. The scales of diseased fish are usually intact and do not fall off. Diseased fish float at the water surface or sink to the bottom, swim slowly, respond sluggishly, and have a poorer appetite.

[Treatment] ① Soak the fish body in a 20 mg/kg concentration of nitrofurazone or furazolidone. When the water temperature is below 20°C, soak for 20-30 minutes; at 21-32°C, soak for 10-15 minutes; used for prevention and early treatment. ② Sprinkle nitrofurazone or furazolidone at a concentration of 0.2-0.3 mg/kg over the whole pond. If the condition is severe, the concentration can be raised to 0.5-1.2 mg/kg; used for prevention and early treatment. ③ Soak the fish body in a 2-2.5 mg/kg concentration of erythromycin. When the water temperature is below 34°C, soak for 30-50 minutes, once a day for 3-5 consecutive days, until the condition improves. ④ Inject streptomycin or kanamycin, injecting 120,000-150,000 international units per kg of fish body weight, usually only once; if the disease is severe, a second injection can be given on the fifth day. ⑤ Oral administration of norfloxacin: use 0.8-1.0 g of powder per 10 kg of fish body weight per day, once a day for 6 consecutive days. ⑥ Soak in a 20 mg/kg concentration of ethacridine lactate. When the water temperature is 5-20°C, soak for 15-30 minutes; at 21-32°C, soak for 10-15 minutes. Used for early treatment with remarkable results. ⑦ Sprinkling at a concentration of 0.8-1.5 mg/kg of ethacridine lactate has a special effect. ⑧ While using the above treatment methods, also carry out a salt water bath, and the effect is remarkable.

[Prevention] ① Reasonable dense stocking, maintaining the dissolved oxygen content in the water at around 5 mg/L. ② Strengthen feeding management and keep the water quality fresh. ③ Periodically sprinkle nitrofurazone or furazolidone over the whole pond to prevent the occurrence of disease.

Red-skin disease (hemorrhagic septicemia)

[Cause] Red-skin disease is caused by Pseudomonas fluorescens. Fish with injured bodies are prone to this disease. Spring and autumn are the epidemic seasons, and it can cause massive fish deaths. This disease is closely related to water quality; it is likely to occur when the dissolved oxygen content is low and the organic matter content is high.

[Symptoms] The skin of diseased fish is locally or largely inflamed and congested, the bases of the fin rays such as the dorsal fin and tail fin are congested, the ends of the fin rays rot, and the mouth cavity and muscles are normal. The scales of diseased fish fall off (which distinguishes it from skin inflammation and congestion disease), most obviously on both sides of the body and the abdomen.

[Prevention and treatment] The same as for skin inflammation and congestion disease.

Enteritis disease

[Symptoms] Caused by Aeromonas punctata. The anus is red and swollen, the intestinal tract is congested and inflamed, and in severe cases the fin bases are congested, red spots appear on the abdomen, ascites flows out when the abdomen is cut open, and the entire intestine is red or purple.

[Prevention and treatment] ① Sprinkle bleaching powder at 1 mg/kg over the whole pond. ② For each hectare with a water depth of 1 m, sprinkle 225-375 kg quicklime over the whole pond. ③ For each 10 kg of fish, use 1 g of sulfaguanidine, made into medicated bait and fed. ④ For each 10 kg of fish, use 50 g of garlic, made into medicated bait and fed, once a day for 3 consecutive days. ⑤ For each 10 kg of fish, use 50 g of dried humifuse euphorbia herb, made into medicated bait and fed, once a day for 3 consecutive days.