Cotton mouth is a highly contagious tropical fish disease that can kill your entire tank if treatment isn’t started immediately. This disease is a bacterial infection that enters through the mouth, gills or wounds in the skin. Fish that have an inadequate diet, live in poor water conditions and are stressed out are at risk for cotton mouth. Contaminated nets, food and containers also spread cotton mouth bacteria.

The most noticeable symptom of cotton mouth is white fungus around the mouth. White spots may also appear on the fins and edges of scales. Infected fish often act listless, loose their appetite and their gills start moving rapidly. Occasionally lesions will start on the back and move down the side, creating a saddle like lesion.

All fish you suspect have cotton mouth should be removed from your main tank to a quarantine tank. You can treat the infected fish by swabbing the mouth with a cotton cloth dipped in very salty water. Or you can put 50 mg of Terramycin or Aureomycuin per gallon of water into the quarantine tank. This treatment is usually very effective and you should see results within 48 hours. Maracyn and Maracyn 2 also stop cotton mouth if the other meds don’t work for you. The temperature of the tank should be lowered as these bacteria reproduce quickly in warm water.

To remove a bacteria from your main tank, change the water, vacuum the gravel and clean any other equipment you use in your tank such as nets and specimen containers before each use.

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