Understanding the Most Common Koi Betta Fish Diseases and How to Treat Them

You love your koi betta fish and want to keep them healthy – but it’s always easy. Koi betta fish are known for being delicate, and they can get sick often. What’s even more frustrating is that their illness usually has something to do with the water, making it harder for you to treat their diseases. Even the most attentive of pet owners may find themselves one day trying to figure out how to help their koi betta fish with a disease. You may have read about other betta fish owners who have struggled with similar things as you, or maybe you just feel like you need a refresher on how to take care of your koi betta fish when it gets sick. The information below should help understand some of the most common koi betta fish diseases and how best to treat them.

Understanding What Causes Koi Betta Fish Diseases

There are many reasons why your koi may get sick, but there are three main culprits you should be aware of: water quality, improper diet, and infections. The first two reasons for disease can be easily avoided with proper care and feeding, but the third reason is a bit harder to prevent. The best thing you can do is to keep an eye on your koi betta fish and learn to recognize the signs of disease. Once you know what to look for, it’s easier to try and prevent it before it happens.

Slimy Koi Betta Disease

Slimy koi bettas are most likely suffering from poor water quality. Water quality is critical to the health of your koi. If the water quality is too low, your koi betta will likely develop an infection or a parasite. If the water is too dirty, the koi betta fish’s immune system has to work extra hard to fight off the disease. If the immune system isn’t working well enough, the koi betta will develop a disease. When a koi betta is suffering from a bacterial or parasitic infection, it has a slimy coat. You can treat this disease by improving the water quality and adding a salt bath to the water.

Cloudy Eye Disease in Koi Bettas

If your koi betta develops cloudy eyes, it’s likely suffering from an infection. You can kill the infection using an antibiotic like Kanamycin. Koi bettas are prone to eye infections because of the way their eyes are structured. Their eyes are on the sides of their heads, which makes it easier for pathogens to reach the eyes.

Fin Red in Koi Bettas

If your koi betta’s fins show signs of redness and you find little red dots on the fins, it’s likely a bacterial infection. If your koi betta has bacterial fin rot, you need to treat it before it spreads to the rest of the koi betta’s body. You should treat fin rot with an antibiotic like Kanamycin. Make sure you follow the directions on the package and don’t use too much of the antibiotic because it can be harmful.

Viral Infection in Kois

A viral infection is an infection that is caused by a virus. Viral infections aren’t always curable, and they can be deadly. Viral infections are common in koi bettas, and they can be difficult to treat. Viral infections are often caused by the goldfish herpes virus. A common symptom of goldfish herpesvirus is the swelling of the head. If your koi betta is suffering from a viral infection, you should put it in quarantine immediately. Don’t try to treat it because it won’t likely help.


Betta fish are popular pets, and they make great choices for beginners. They are easy to care for, and they don’t require a lot of attention. Even so, some common diseases affect koi bettas and can make them sick. If you want to keep your koi betta healthy, you need to know how to recognize the signs of a disease and how best to treat them. It’s also important to make sure your koi betta has clean water. That way, you can prevent diseases before they happen and keep your koi betta happy and healthy.