How to Care for Koi Fishes

As with any pet, taking care of this fish requires a basic understanding of their natural habitat and favored conditions. Koi are freshwater fish that require a cool (about 68°C; not less than 50°F), ambient temperature, and a large aquarium.

On the other hand, if you are keeping them in an aquarium, make sure it is at least 6 feet tall, and more than twice that in length. If the temperature becomes lower than 50°F, their immunity system stops working and certain health issues may arise in their digestive systems.

Koi can be wonderful companions―they recognize their feeders, and can even be trained to feed from the owner's hands―but maintaining healthy conditions for the fish can be tricky. Genetically, koi are a tough, enduring species, and are resistant to most diseases. So, the environment plays a huge role in determining their longevity.

One of the most important factors is maintaining the water quality. Regulate the temperature, light condition, and nutrient concentration (nitrites, phosphates) as per the seasonal needs.

The pH range should be between 7 to 7.5. Installing a pump and skimmer system is a basic necessity prior to introducing the fish in a pond or fish tank. The water quality should be monitored regularly; you can replace about 20 percent of the tank water at least once in two weeks time.

Also, the protein content of the foods differs for each growth stage; young koi require higher protein, while older ones can be given less protein. The amount of food should be such that they are eaten within a few minutes. Otherwise, as the fish are heavy feeders, they can eat excessively.

In addition, fallen fish foods may degrade and disturb the water chemistry. Apart from formulated foods, koi will enjoy an occasional fruits and leafy vegetables, since they are naturally omnivorous feeders.

Before you purchase the fish, make sure that you select the number as per the size of the pond or fish tank. You can also consider the size of the fish that you are opting for. On an average, a full-grown koi fish can be reared in a water capacity of about 100 gallons.

Accordingly, estimate the number of koi with reference to the total water in the fish tank or pond system. An overcrowded system results in an unhealthy water quality and/or environmental condition for the inhabitants.

In case of any irregularities in the water chemistry or nutrition, the fish will become inactive and dull. In severe cases, their health may deteriorate due to the bacterial infections. Diseases may also result from the introduction of other diseased fish or damaged plants.

You can check for occurrence of bacteria on the underside of the belly. In case you find sick koi, separate them from the rest of the population and change the water as soon as possible. This will prevent further spreading of the disease.

Koi fish can survive up to 40 years, provided that the right environmental conditions are maintained. Though you may require patience and continuous efforts to keep koi fish in the aquarium, the satisfaction of watching them playing is worth taking up the hurdles.