How Long do Koi Fish Live & What Affects Their Lifespan

koi fish swimming in a pond

If you have a pond and are thinking about buying some koi fish, you may be wondering how long they live. A quick search tells you they can live to be 100 years or older! While this might be great for some people, it may sound daunting for others.  Don’t worry, as not all koi fish live that long. 

Contrary to popular belief, the level of care and pond conditions mainly determine a koi’s life span. 

How long they live depends on certain variables; the health of the fish, its diet, water temperature, and the quality of water. Koi continue to grow and get older until they have reached their genetic age and size. On average, koi fish can live for 20-30 years or even 60 years.

Koi lifespans will vary based on three variables:

  1. Koi maintained in perfect conditions, with optimal pH levels, water quality, nutritional status, and low stress, they could remain healthy into their 60s, 50s, and even into their 90s. A few outliers, such as Hanako, were said to have had lived for 226 years (more information below).
  2. Koi fish that are not taken care of optimally usually live shorter. For instance, owners might struggle to master the essential information about the hobby within three to five years. 
  3. Since 25 years is a long time.  Many things can affect the quality of a koi fish’s habitat, such as power outages, low water conditions, water temperatures, etc.

Breeding also affects koi fish lifespans. Domestic koi in the USA may only live around 15 years, whereas high-quality Japanese koi called nishikigoi can live to be 40 years old or more. 

Other Factors That Determine How Long Koi Live

Since we now know that the conditions are such a big part of how long a koi fish lives- let’s go over the essential points.

Nutrition

It has been observed that the high nutrient koi food can play an essential contribution to koi’s overall health and development.

Therefore, it is necessary to be aware of your options and read the labels attentively before buying food for your koi.

Here’s what you should look for in koi food.

  1. Protein, for example, soya meal or fish meal.
  2. Fats should be 10% for young koi and 33% for adult koi
  3. Carbohydrates, such as soybeans, rose hips, wheat, and corn
  4. Minerals and vitamins like Calcium, magnesium, sodium, etc.

Apart from store-bought koi food, koi enjoy orange peels, rice, peas, and shrimp.

One aspect essential to an overall healthy koi life is bonding with the owner. Koi are docile, social animals that can respond to humans. Thus, feeding time is perfect for connecting with your koi by feeding them by hand.

It’s always enjoyable to interact with koi. Once you can hand feed them, note how they perceive your presence as their caretaker. It’s something to be proud of!

Pond Water Oxygen Levels

The main factor contributing to the depletion of oxygen in koi ponds is the growth of algae.

Algae make oxygen during the daytime as a result of photosynthesis. When algae grow beyond control, they will take oxygen, which could cause the fish to die.

Another aspect that can affect the oxygen concentration within the koi pond is the sudden disappearance of algae. The algae may die from natural causes or any chemical that kills algae. As the algae die, they lose oxygen and could also change water oxygen levels.

The best solution is testing equipment that can precisely measure dissolved oxygen levels.

In addition, to keep oxygen levels high, you should install air diffusers and pumps that release the oxygen and circulate the entire volume of pond water.

Also, to avoid huge algae blooms or green water, consider adding an ultraviolet sterilizer to your pond.

Fish Genetics

However good the conditions of your pond are, nothing can beat genetics.

Japan is leading the way in koi development.

Although koi breeders have done their best to improve their gene pools, Japanese koi live longer than the typical domestic koi found in pet shops.

Many of the best koi breeders use imported koi or are part of significant genetic lines and breed off of it.

A reputable breeder will ensure the quality of koi you will receive and contain a mix of imported Japanese koi and domestically bred Koi.

Pond Water Quality

Your pond water must be high-quality if you wish your koi to live a long, happy life.

The water you provide for your koi must be free of ammonia, chlorine, nitrates, and nitrites to ensure the highest fish protection from bacterial skin diseases.

You can ensure the water’s quality by conducting regular tests and using high-quality pond filtration.

Winter

Koi are cold-water fish that can withstand extreme temperatures when ponds are correctly winterized.

Preparation is critical, though.

Koi fish hibernate in the winter months. This process is a significant factor in the long life span of koi. The hibernation process occurs when temperatures are below 50 degrees. In which they reach a state known as torpor (science direct).

Many novice keepers move their fish inside or even insulate their outdoor pond until it exceeds 50 degrees F.

While you may think this is best, it isn’t advised.

To help your koi remain healthy and happy, it is recommended to let them hibernate in winter and use a pond de-icer and air pump.  This allows proper gas exchange and oxygen levels.  

Frequently Asked Questions

What is the oldest koi fish?

One of the oldest koi fish that has ever existed to date is known as Hanako.

Hanako was female koi fish that was colored scarlet. The most exciting thing is that, in general, the lifespan of scarlet koi is about 40 years. But, Hanako weighed 7.5 kg and was 226 years old by the 1970s.

Doctor. Komei Koshihara, Hanako’s previous owner, had her age verified by professor Masayoshi Hiro. Hiro took two scales from Hanako to establish her actual age.

Dr. Komei Koshihara claimed that Hanako and he was close friends with a beautiful relationship. In a radio program in 1966, doctor. Komei Koshihara said, “When I call her (Hanako) saying ‘Hanako! Hanako!’ from the brink of the pond, she unhesitatingly comes swimming to my feet. If I lightly pat her on the head, she looks pretty delighted. Sometimes I go so far as to take her out of the water and embrace her.”.

Hanako was passed down to the generations of the Koshihara family. Unfortunately, in two centuries, two decades, and six long years, Hanako passed away in Japan on July 7, 1977.

How long do koi fish live in the wild?

In the wild, koi fish are believed to live for 15 up to 20 years, with male koi having longer lives than females. Japanese koi generally live for longer due to the superior genes they possess.

Conclusion

Koi fish are a popular choice for many homeowners looking to add a little bit of beauty and serenity to their backyard. These elegant creatures come in a wide variety of colors and patterns, and they can live for many years with proper care.

On average, koi fish live between 20 and 30 years, although some individual fish have been known to live for 40 years or more.

Koi are very resilient and can withstand a wide range of environmental conditions but thrive when given plenty of space to swim and clean, oxygenated water.