A Quick Guide to Common Koi Fish Diseases


Your Koi is a unique species of aquatic life.

The Koi fish symbolizes friendship and love.

It is a popular fish that developed long ago in the 1820s in Japan.

They are sometimes known as Japanese Carp.

There are several colors and varieties available in the Koi.

This fish is often found in an outdoor pool for decorative purposes.

Koi fish can be subject to many different types of koi disease that can be harmful.

It is important to inspect your tank regularly and be alert to the different signs and symptoms of these different diseases.

Treatment for these koi diseases should be started as soon as a problem is recognized.


If your Koi has any indication of a circular area around an open wound, it could be cancer.

This type of Koi disease is indicated by a white color with the center being pink.

The treatment for this Koi disease is removal of the cancer tissue.


An open wound that is discolored on your fish could indicate Koi disease infection.

Removal of the dead skin surrounding the area is recommended to prevent further infection and to promote healing of the area.

You can help your Koi by taking a piece of gauze and rubbing the area.

This has to be done extremely gently.

A soft toothbrush will work well also.

The Eye

A Koi with an eye disease is quite noticeable.

A common Koi disease of the eye is called Popeye or exophthalmia.

It is characterized by a protrusion of the eye from the eye socket.

The cause of this likely stems from either tuberculosis or a mycobacterial infection.

This is encouraged secondary to an eye granuloma, an eye abscess, a choroid infection, a viral infection or trauma.

An eye Koi disease can be difficult to resolve as the Koi’s eyes have a limited vascularity.

The medications used to treat an eye disease in the Koi are not highly receptive to this area.

Tuberculosis in a Koi fish can be transmitted to humans.

Caution when dealing with this problem is highly recommended.

The Mouth

An ulcer or an abscess may be found in some Koi fish.

Your Koi will have difficulty closing its mouths if he comes down with this affliction.

This ulcer or abscess will most likely have come from a bacterial infection.

The infection travels through the mouth region and inflames the ligaments of the Koi fish’s mouth.

Starting your Koi fish on an antibiotic as soon as possible is ideal.

However, permanent damage to your Koi may already have taken place.

Enjoy your Koi fish and act upon the first sign of any illness to avoid further koi disease of your favourite pet.

Always consult your local vet or koi expert if you are in doubt at all. It could be disastrous to leave any koi disease untreated.

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