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Ulcer disease is one of the most common conditions of Koi carp and goldfish observed by the VSD Fish Diseases Unit diagnostic service. Skin lesions such as ulcers or sores on the body, reddening at the base of the fins and the vent, loss of appetite and darkening of coloration are all symptoms of infection.


  • Elevated scales

  • Increased redness to veins (erythema)

  • Scale loss

  • Red spots (varying sizes)

  • Skin erosion



    Use anti Ulcer medicines according to the tank size (Dosage 10 ml per 100 liters)


    If the fish are still feeding, a full course of antibiotic medicated flake or pelleted feed can be very beneficial. A course of antibiotic injections is the treatment of choice if large or very valuable fish are involved; bath treatment is generally not worth the cost and is often ineffective.

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