My mother has had a koi pond for over 12 years. In the last 6 months she has noticed that her large koi have developed ulcers which seem to have spread to all her fish. She bought 4 small koi from a reputable dealer which started with ulcers. She complained and took the fish back but noticed shortly afterwards that the other fish started getting ulcers.
We have treated the pond with different medicines but have not noticed any difference in the fish. Some of the fish are over 20 inches long and we are worried that she may loose some of the.
Do you have any suggestions please on how to treat the fish?
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It sounds like your fish may have fish tuberculosis.