Koi have a heritage of activity and they will tend to hurt themselves by jumping and hitting rocks. If they are healthy and water conditions are good, most of the cuts and bruises will heal naturally. However, if the koi are not healthy and if the water conditions are bad, these cuts and bruises become a problem with secondary infections setting in due to bacteria and germ invasions. "Hole in the side" can begin with this type of injury.

Painting Mercurochrome on small cuts and bruises should be sufficient treatment to prevent secondary infections. When severe cuts and bruises get infected, and antibiotic injection is most effective. A chemical bath to treat an infection is not as effective as antibiotic injections.

*Information on this page is an excerpt from "KOI" by Grant Fujita, available at the AKCA online bookstore.