Koi Mold is a bacterial infectious disease that usually manifests itself when koi are kept in poor living conditions or when the fish become stressed due to a sudden deterioration in water quality.

In this disease, whitish, mossy patches form that first appear around the mouth (hence the name) and later spread all over the body and fins. Often they lead to ulcers, and the fish looks thin.

The disease is caused by the bacterium Fexibacter, which under the microscope typically looks like a colony of fairly long thin rods that contract and move smoothly. Flexibacter is common in warm water that contains a lot of organic material, and will quickly spread from one fish to another in these circumstances.

Treatment with an antibacterial agent is usually sufficient.

Treatment: see Products: Medicines; Alparex, Cytofex, Lernex, FMC50, Acriflavin, Malachit, Malachite Green, Formaldehyde, FMGMix.