Mouth Disease in Tropical Fish

Five common diseases affect the mouths of tropical fish: lymphocystosis, tremode infestation, lateral line disease, vibriosis and cotton mouth. Stress in the tank can contribute to these diseases.

  1. Lymphocystosis

    • Lymphocystosis (knot disease) is caused by the virus Lymphocystis. You might notice white, knot-like or cauliflower-like swellings around the mouth and edges of fins and gills. It is not a serious condition, nor is not highly contagious.

    Tremode Infestation

    • Tremodes are small parasitic worms that infect the mouth, skin, gills, eyes and anal opening. You can suspect a tremode infestation if your fish rub themselves along rough edges in the aquarium. That can lead to bacterial infections that are more serious than the tremode infestation itself.

    Lateral Line Disease

    • Fish with lateral line disease develop small holes in the sensory pits of their heads and along the lateral line of their bodies that enlarge as the disease progresses. Bacterial infections of the holes can kill the fish.

    Vibriosis

    • Vibriosis or ulcer disease is caused by Vibrio bacteria. Ulcers develop on the lower jaw, along with other symptoms such as bleeding from the gills and lethargy.

    Cotton Mouth

    • Cotton mouth is caused by the bacteria Chondrococcus columnaris. It begins with a white line around the lips and then develops into a cottony tuft from the mouth. Cotton mouth will kill the fish unless you catch it early.