How to treat Columnaris

Columnaris (also referred to as cottonmouth) is a symptom of disease in fish which results from an infection caused by the Gram-negative, aerobic, rod-shaped bacterium Flavobacterium columnare. Columnaris is a deadly and fast-moving infection that can wipe out an entire tank if not treated correctly and swiftly! Columnaris only affects freshwater fish, both in the wild and in aquariums. It cannot live in aquarium salt water.


Here at Colorz Guppy Farm I have dealt with columnaris many times after importing fish and the treatment I have found to be most effective is using Salt and Methylene Blue along with my General Medicated flake or pellets and then followed up with the Nitro Supplement food.


  • Turn off your heater and lower water temp to room temp. (20-22C)
  • Do a 50% water change.
  • If you use a water conditioner like Prime or Aqua Safe, wait 45-60 minutes before adding treatment.
  • Add the salt and Methylene Blue to the tank.
  • Wait 7 to 10 days with no water changes. (feed General Medicated flake or pellets sparingly.)
  • After 7 to 10 days do a 50% water change. If fish are cured.
  • If it is not cured, do a 2nd treatment and do a 50% of the original amount dosed and wait for another 5 to 7 days.
  • If no signs of Columnaris, leave the 50% salt and Methylene Blue in the tank until your next water change time. Do 50% water changes at your normal water change times until all the blue is gone from water. Or simply add activated carbon media to a filter to remove the blue color from the water!

* Once your Guppies are better and recovering I suggest to give them Nitro Supplement more often (2 times per day) for the next 2 weeks and then return to your normal feeding. Nitro Supplement is what I use to help boost their immune system.


Thats it! I hope that helps you 🙂



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