Cotton Fungus in Fish

Cotton fungus usually attacks weak, infected or injured fish. If left untreated, these fish die and can affect aquarium mates. Although very common, cotton fungus is a very serious fish disease that can eliminate entire tanks. Owners should have the ability to quickly assess their fish to determine if they have cotton fungus or not.

  1. Identification

    • Cotton fungus, or cotton wool disease, usually first shows up in a previously injured area. Fish owners should closely watch these areas for changes. Cotton fungus begins as white fluffy cotton-looking growths. If left untreated, it spreads to the mouth, fins and the rest of the skin, according to the website Pet Education.

    Risk Factors

    • Cotton fungus appears commonly in aquarium fish. Some things, however, make a fish tank more likely to house the disease. Poor, or unchanged water makes cotton fungus more common. Also, aquariums with dead or injured fish tend to infect others with cotton fungus, says Pet Education.

    Danger

    • The fungus Saprolegnia most commonly causes cotton fungus in fish. The cotton-looking fungus breaks down the skin and tissue surrounding it and then begins absorbing necessary nutrients, carbohydrates and protein from the fish. Eventually, without treatment, the fish dies, according to Fish Lore.

    Treatment

    • Cotton wool disease often infects entire tanks. When that happens, the fish all require salt baths and anti-fungal medication, says Pet Education. Also, the tank water needs changed as soon as a fish shows signs of the disease. If only one fish shows symptoms, and the owner acts quickly, that fish can receive sole treatment in a separate tank.

    Considerations

    • In more serious cases, cotton wool disease affects fertilized and unfertilized eggs as well as fish. Nothing properly treats fish eggs for the condition, so the tank owner must immediately dispose of them before they infect further eggs, according to Pet Education.