(1) Symptoms:
The skin shows inflammation and congestion. In severe cases, fin rays may rupture. Internal organs such as the intestines, kidneys, and liver exhibit varying degrees of inflammation. Affected fish may float on the water surface or sink to the bottom, swim sluggishly, respond slowly, and may die in severe cases.
(2) Preventive Measures:
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Improve husbandry management. Feed more live animal-based foods such as daphnia, chironomid larvae, and tubifex worms, supplemented with a small amount of Wolffia (watermeal) to boost disease resistance.
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Bathe the fish in nitrofurazone or furazolidone solution at a concentration of 20×10⁻⁶ mg/L. Soaking duration: 20–30 minutes when water temperature is below 20°C, and 10–15 minutes at 21–32°C.
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Extend the lighting duration in the aquarium.
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Maintain dissolved oxygen levels in water at around 5 mg/L.
(3) Treatment Methods:
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Apply nitrofurazone or furazolidone throughout the pond at a concentration of (0.2–0.3)×10⁻⁶ mg/L. In severe cases, increase the concentration to (0.5–1.2)×10⁻⁶ mg/L for better efficacy.
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Bathe the fish in erythromycin solution at a concentration of (2.0–2.5)×10⁻⁶ mg/L for 30–50 minutes, once daily for 3–5 consecutive days.
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Administer streptomycin or kanamycin via injection. Dosage: 120,000–150,000 IU per kilogram of koi intraperitoneally, with an additional injection on the fifth day if needed.
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Dissolve 0.2 grams of nitrofurazone powder and 250 grams of salt in 10 kg of water, and bathe the sick fish for 10–20 minutes.
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Bathe the sick fish in a 5% potassium permanganate solution for 10 hours.
