How to Treat Mouth Fungus in Fish

Mouth fungus in freshwater fish is not actually a fungal infection, but is instead a bacterial infection caused by the flexibacter bacteria (see reference 1). Fish afflicted with this bacterial disease will show symptoms including a white substance around the mouth that will become fluffy, resembling cotton. The fish may become lethargic and stop eating. Left untreated, mouth fungus can be fatal (see reference 2).

Things You'll Need

  • Aquarium Test Kit
  • Water conditioner or de-chlorinator
  • Antibiotics
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Instructions

    • 1

      Identify any fish infected with mouth fungus and make note of their symptoms to track treatment progress.

    • 2

      Do a partial water change, making sure to add de-chlorinator or water conditioner to new water. Bacterial infections such as mouth fungus are usually a sign of poor water conditions and a clean environment will help the fish fight infection (see reference 1).

    • 3

      Buy an aquarium test kit, test the water, and correct any incorrect chemical levels with commercial products, such as pH increaser or reducer. The test kit should come with instructions explaining what chemical levels are correct for the aquarium.

    • 4

      Remove the carbon filter from the aquarium's filter system. The carbon filter may remove medication from the water, making it less effective.

    • 5

      Add an antibiotic to the water such as penicillin, chloromycetin (see reference 2), or another commercial product for the treatment of mouth fungus.

    • 6

      Treat the water a second time in 48 hours (see reference 2).