Mouth Fungus in Fish

Fish make colorful, interesting pets but like all animals they can become ill. Mouth fungus is a common fish ailment but the numerous varieties and causes can make it difficult to treat.

  1. Mouth Fungus

    • Fungal infections are often caused by fungi of the order Saprolegniales. These fungi attach to a host fish and form a pale, fluffy substance on the scales, gills, fins and mouth of the fish. Because of the color and texture of this fungus, an infection is often called cotton wool disease.

    Mouth Rot

    • Mouth rot is actually a bacterial infection caused by Flexibacter columnaris. It is often confused with a fungal infection, as the shape and behavior of the bacteria gives the fish a fluffy appearance.

    Causes

    • Past injury, parasites, stress and poor water quality are common causes of mouth fungus in fish. Fish are most susceptible when their immune systems are weak.

    Treatment

    • Treat mouth fungus with aquarium antifungal medications and treat bacterial mouth rot with aquarium antibacterial medications. Severe cases of bacterial mouth rot require antibiotics.

    Prevention

    • Maintain a clean tank with weekly partial water changes, and test your water for ammonia and nitrites regularly. Quarantine new fish before adding them to your tank, and separate any fish that are fighting.