cotton mouth disease fish

Cotton Mouth Disease In Fish

Are you looking to find out more about the cotton mouth disease? 

cotton mouth disease fish

In that case, you are in the right place!

Columnaris or cotton mouth is a disease in fish is a result of an infection caused by the gram-negative bacteria that are found almost everywhere on the planet.

These bacteria are present in freshwater which makes this disease highly contagious.

The consequences of cotton mouth disease can be fatal.

In this article, we will go through everything you need to know about the cotton mouth disease in fish including causes, symptoms, and treatment of the disease in as much detail as we possibly can.

So, without further ado, let’s jump right in.

Here we go.

Quick Note:

Cotton Mouth is also referred to as cotton wool disease, saddleback disease, and guppy disease.

What Causes Fish Cotton Mouth Disease?

Columnaris or cotton mouth disease, as we mentioned above, is caused by a gram-negative bacteria called bacterium Flavobacterium columnare.

The bacteria infects fish that are stressed by poor living conditions including stress due to shipping and handling, poor water quality, and even an inadequate diet.

These bacterias can enter the fish via the mouth, small wounds on the skin, and gills.

The Columnaris bacteria can stay in the water for as long as 32 days--especially if the hardness of the water is 50 ppm or more. Cotton mouth disease is a highly contagious one and spreads via specimen containers, food, and contaminated nets.

So, it is crucial to avoid contaminating other tanks by using sterile techniques.

For tanks that share a common filtration system, we recommend that you use a prophylactic treatment to ensure that your fish are not exposed to the disease-causing bacteria.

Moving on.

Common Symptoms of Cotton Mouth Fish Disease

In this section of the article, I would like to go through some of the common symptoms of cotton fish mouth disease.

Let’s begin.

  • Frayed and ragged fins
  • White or cloudy, fungus-like patches – especially on the gill filaments
  • Loss of the epidermal layer
  • The appearance of ulcerations on the skin
  • Necrosis on the gills
  • Mucus accumulated on the head, gills, and dorsal regions
  • Changed color of the gills---light or dark brown
  • Lethargy
  • Anorexia
  • Mortalities in young fish
  • Rapid and laborious breathing which signifies gill damage

Treatment Options For Cotton Mouth Disease

There are a few treatment options available for cotton mouth.


Antibiotics is our first option.

You can treat the fish using a combination of antibiotics such as kanamycin and nitrofurazone. These can be administered to the fish synergistically.

Fish Bath

Running a fish bath medicated with merbromin, salt, potassium permanganate, or methylene blue helps in

Lowering the temperature

The columnar bacteria thrive at a higher temperature so, lowering the temperature of the aquarium to 75 °F is an excellent way to control the disease

Medicated food

Feeding fish food that contains oxytetracycline to control the internal infections

Summing Up: Fish Cotton Mouth Disease

Cottonmouth is a highly contagious disease found in fish. The disease is a result of an infection caused by the gram-negative bacteria which are present in freshwater. The consequences of this disease can be fatal.

As aquarium enthusiast we must be proactive in preventing cotton mouth and all other ailments our fish can suffer from.

We can prevent these issues by maintaining proper water quality, feeding fish appropriately, housing the correct amount of fish in a fish tank and conducting regular water checks.

With precaution and proper treatment, the cotton mouth as well as other diseases, fungus and bacteria can be prevented or controlled.

Have questions? Let us know in the comments.