Koi Fungus infections

Fungus under the microscope

Fungus infections are common in Koi that are too cold, or are severely stressed. You can look at a Koi with fungus and safely assess that it's got a SEVERELY compromised immune system. It's NORMAL for fungus to grow in existing or even healing bacterial sores. If the fish is schooling with the rest of the fish and still taking food, NO treatment is usually indicated for mere patches of fungus. If the fish is showing signs of "losing" the battle to the fungus, it should be brought gently to 76-78 degrees Fahrenheit, one degree per hour until the goal temperature is accomplished. Aeration should be supplemented to these fish. Gentle handling is critical as the fish with fungus is by definition "In a Weakened Condition" or it would not be growing fungus organisms in its skin defects.

Fungus patch in Goldfish wound.

Warmed and fed medicated fish food, a fish with some fungus patches should do very well. If you desire to kill off some of the fungus or reduce the fungal colonies, you can swab the lesions with 3% hydrogen peroxide, potassium permanganate or even methylene blue. Return the fish to the water quickly and handle it as little as possible. Wear eye protection if you are using something caustic to your eyeballs, as Murphy's Law holds that the fish WILL thrash anything you put on it's body into your eyes.

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