What Can I Do to Identify and Treat Koi Fin Disease?

What Can I Do to Identify and Treat Koi Fin Disease?

Having a sick pet is arguably one of the most stressful things in the world.

Animals cannot easily tell you exactly what is wrong, making it quite hard for even professional veterinarians to pinpoint exactly what is making your pet feel under the weather.

Fortunately, with koi fish, there are a lot of wide-spectrum treatments that can be done to help remedy health issues, especially if they present themselves on the skin or fins of the fish.

Let’s take a look at some of the best ways to identify and treat koi fin disease to get your friend back together in no time!

koi fin disease

Types of Koi Fin Diseases

There are many different koi illnesses that can cause a reaction that results in lasting fin damage.

Let’s take a look at each and what treatments are effective in remedying the illness once and for all.

koi fin disease

Fin Rot

While technically not an illness in and of itself, fin rot is a secondary sickness that is a symptom of a larger illness or issue. 

Still, it can be painful and have a massive impact on your fish and should be taken very seriously.

Typically, fin rot is caused by stress or poor water quality; the source is typically bacterial.

Usually, you can treat fin rot with the help of adding a small amount of aquatic salt to your koi pond or removing the impacted fish from the pond and placing them in a separate quarantine tank to give it salt baths.

Either way, salt is key in killing off the bacteria; just follow the directions closely to ensure your koi are safe and healthy during their treatment since salt with a freshwater fish can be detrimental if dosed too heavily. 

koi fin disease

Koi Herpes Virus

KHV or Koi Herpes Virus is a viral illness that is highly contagious and can spread quickly through an entire pond ecosystem.

The biggest symptom of koi herpes virus is the skin of the fish peeling or sloughing off, revealing the delicate and sensitive tissues underneath. 

They will also have lesions and tearing on the fins and gills, as well.

This is a very serious illness and must be treated immediately in order to prevent death.

To do so, dose with salt and increase the temperature of the water to kill off the virus (do this under the guidance of a reputable breeder or veterinarian).

You also likely need to seek out anti-viral koi food to help prevent further infection.


Another common illness that can be very serious, Costia is caused by a parasitic infection.

Costia are tiny parasites that generally impact immunocompromised fish in the spring.

They cause itching and you may see your koi attempting to scratch itself on the pond and rocks. 

There will also be reddening of the fins and gills and even lesions on the fins.

Malachite green, formalin, acriflavine can all be used to treat costia but you must make sure there is no salt in the water to prevent a chemical reaction that could potentially put your koi population in danger from occurring.

Separately, you can give your koi salt baths, as well, to further the treatment, just do not mix the medications with the salt. 

Fungal Fin Disease

There are many different types of fungal infections that can cause koi fin diseases.

You will likely see raised bumps or green, fluffy growths on the fins of your koi, which can make moving sometimes quite painful.

Fortunately, you can treat fungal disorders rather easily and do not have to worry about it spreading rapidly through the population if you catch it early enough. 

To treat it, simply wipe away any of the visible fungal growth with a clean q-tip. 

You should then apply an antibiotic ointment to assist in preventing the further spread and growth of more fungal areas on the koi’s body.

Fungal infections are usually not fatal and are rather easy to treat if you find the issue early on, so be sure to regularly check on your fish and always make sure to monitor their overall health and wellbeing to look for potential issues. 

koi fin disease

More Serious Issues

There are more serious issues that can cause koi fin diseases and erosion.

For these illnesses, veterinarian assistance is needed, as the treatment can involve regularly administered injections until the disorder is gone.

The resulting issues can trigger other disorders as well, making the vet help absolutely crucial if you have any hope for your fish’s potential recovery.

This can be costly and sometimes still result in a need for euthanasia but, as a whole, veterinarians can assist you on the best possible treatment options you have in looking to remedy the issue and do what is best for your koi in the long run. 


Sometimes, the source of the issue is not an illness or koi fin disease at all, but instead an injury.

This could be caused by inappropriate tank decor or fighting with other koi. 

If you notice cuts or other issues on your koi’s fins, try cleaning the area and removing any potentially damaging rocks or other sharp decor pieces to prevent future injuries.

The koi may also need assistance if the injury is particularly bad, so do not hesitate to contact a veterinarian if need be to ensure your koi is getting the best care possible given their current health status.

Sometimes stitches, trimmings, or other procedures must be performed and most vets will recommend keeping the injured koi quarantined until it is back to normal so if the injury is bad, do not hesitate to make the call to a professional. 

koi fin disease

Health and Happiness

Koi fish are incredibly hardy pets that can handle a lot.

They rarely get sick to the point that you should be concerned they may die but you should still treat them as soon as you notice an issue and always strive to provide them with the best possible quality of care.

If you do this, they will likely be back to normal in no time!