How Long Do Koi Fish Live? Lifespan, Care, And More
Koi fish are some of the hardiest freshwater fish you can keep in an aquarium. Being a pet koi fish owner comes with a great deal of responsibility, not because they are high-maintenance, but because their life expectancy is longer than that of most pet fish. How long do koi fish live?
Koi fish will live 25-35 years on average while in captivity and being provided with optimal care. The better you take care of your koi, the longer they will live.
A koi fish’s lifespan depends on a lot of external factors that we’ll get into later in this article. Caring for a koi fish for several decades will reward you with a spectacular view, as koi fish come in stunning varieties with a dragon-like appearance.
If you stay proactive in interacting with your pet koi fish, they can learn to recognize you as their owner and view each feeding as a positive reinforcement to interact with you, much like a house pet would.
Koi Fish (Cyprinus rubrofuscus)
| Care level | Medium difficulty |
| Temperament | Peaceful |
| Size | 24 to 36 inches (on average) |
| Diet | Omnivorous |
| Family | Cyprinidae |
| Minimum tank capacity | 55 gallons as juveniles – 200 gallons when mature |
| Tank Set-Up | Freshwater with muddy substrate |
| Tank Mates | Other peaceful fish |
There are quite a few factors that will determine how long a koi fish lives, ranging from its genetics, its owner’s experience level, and the conditions of its environment in captivity.
- Domestic koi fish – which are koi varieties commonly found in western aquariums, have an average lifespan of 15 years.
- Japanese koi fish – which are bred from ancient Japanese gene pools, can have an average lifespan of 40 years, with some living well into their 60s.
Novice fishkeepers will inadvertently shorten their koi fish’s lifespan down to about 3-5 years simply because they lack the knowledge required to create, and sustain, an environment that would allow a koi fish to live longer.
An experienced koi owner can give a koi fish the ideal conditions to live an average of 25-35 years. In this case, if you introduce a koi juvenile into your aquarium, you’re likely to have a lifelong pet.
How To Increase Koi Fish Longevity – Ideal Tank Conditions
Because koi fish have significantly longer lifespans than most aquarium fish their size, they are a pet fish you’ll need to commit to when becoming their owner.
These ornamental carp beauties are low-maintenance and resilient to most environmental conditions. Still, they need to receive proper care if you want them to become your lifelong pet fish, with a 25–35-year lifespan.
Here’s how you create the ideal tank conditions to increase a koi fish’s longevity:
Tank size and set-up
Koi fish are extremely active and will swim during the day and sometimes through the night when looking for food.
The ideal tank size for pet koi fish will depend on the variety of ornamental carp you own, but here are some guidelines you can follow:
- Juvenile koi fish can be kept in 30-50-gallon tanks;
- Mature koi fish will need at least 100 gallons of water per fish in a 36-inch deep pond;
- Mature koi fish will need 200 gallons of water in an aquarium for a single mature koi fish;
- For a group of mature koi fish in an aquarium, you will need a 1000-gallon tank that’s 72 inches deep.
Place your koi fish tank away from direct sunlight and any drafty spots.
Keep a lid on your aquarium at all times because these messy freshwater fish will splash.
When introducing new koi fish to a tank, try to add as few as 2 or 3 individuals at a time, especially if they’re fully matured. They can be very messy, and the sudden influx of additional waste can trigger a bacterial imbalance even in a well-established tank.
Filter and water quality
You’ll need a strong filtering system to cycle the entire capacity of your koi fish tank at least three times per day. Koi fish are resilient enough to survive in environments with poor water quality, but they are still susceptible to ammonia poisoning (levels as low as 0.25 ppm can be deadly!).
Temperature
When kept in a pond that’s deep enough, koi fish will hibernate under ice in the winter and slow down their metabolism to survive. This can significantly increase their longevity.
Inside a koi fish tank, you should keep the water temperature between 65-75°F.
pH
Keep the pH level anywhere between 7.0-9.0.
Lights
Keep a koi fish tank illuminated on a diurnal schedule, with 8-10 hours of daylight per day.
Outdoor koi ponds need to have shaded areas for your koi fish to retreat to during torrid summer days.
Substrate
Put a generous layer of muddy substrate in your koi fish tank to mimic the natural environment that carps thrive in when in the wild.
Most koi fishkeepers avoid adding aquatic plants to their koi aquariums because they will be up-rooted by the constant digging.
Diet
Koi fish are greedy eaters, and telling how much food is too much can be hard with aquarium fish this size. To increase their longevity, Japanese koi fishkeepers advise against overfeeding.
Obesity and constant overfeeding will significantly shorten a koi fish’s lifespan.
Why Do Japanese Koi Fish Live Longer?
Japanese koi holds the record of “longest recorded lifespan” for any ornamental carp variety.
The oldest recorded koi specimen was called Hanako, and it lived in Japan, reaching the ripe age of 226.
Hanako died of old age in 1977, measuring 27 inches. Her age was determined using the rings on her scales, much like one would assess a tree’s age.
Learn more about the history of Hanako here:
Of course, Hanako’s outstanding longevity isn’t the norm among Japanese koi fish, but they do have the longest lifespans among all koi varieties.
So, why do Japanese koi fish live longer than other ornamental carp varieties?
- Koi-raising knowledge in Japanese culture
Western fishkeepers are significantly less experienced in raising traditionally-Japanese koi varieties.
Meanwhile, Japanese culture has the upper-hand in raising koi, with knowledge being passed down through generations of koi fishkeepers.
For one thing, western koi breeders are hyper-focused on creating rapid-growing koi fish varieties, which in turn has significantly shortened the average lifespan of domestic koi varieties.
- Ancient Japanese Koi genes
Japanese rice farmers were the original breeders of the modern Japanese ornamental carp varieties, which means they had the chance to hand-pick only the greatest koi specimens, keeping the koi gene pool diverse and immaculate.
Even as koi fishkeeping reached the western world, the highest quality Japanese Koi never left their homeland.
- Hibernation in Japanese Koi
A Japanese koi fish’s life cycle is known to include periodic stages of hibernation during harsh and cold Japanese winters.
Living in a colder environment, and slowing down their metabolism for several months each year, is one of the most substantial factors that influence the longer lifespan of Japanese Koi.
Hanako herself lived to see her 226th birthday because she was raised in a cooler environment, hibernating during winters.
Koi Fish Care
Behavior and temperament
Koi fish are peaceful by nature, doing best in groups of 5-15 fish. Large groups of koi fish should only be kept in ponds, as they need a lot of room to swim.
They are extremely active and will be on a constant search for food, exploring all levels of an aquarium.
Koi fish kept in an aquarium tend to dig at the substrate between feedings, so they’re considered messy pet fish.
When kept in a pond, koi fish will interact with people that they learn to associate with food and can be hand-fed when enough trust is gained.
Most koi fish varieties kept in an outdoor body of water will “hibernate” at the bottom of the pond, where they will still actively swim and munch on algae.
Size
The size of a mature koi fish depends greatly on the variety of koi in question. On average, a koi fish will grow between 24-36 inches in length.
The typical western domestic koi fish will have a size between 12-15 inches when reaching maturity, while Japanese koi grow up to be 22-26 inches long. Jumbo varieties of koi will grow to be as long as 34-36 inches.
So, they’re definitely larger than most pet fish that you can keep in a tank. On the bright side, they’re also much easier to care for than other larger aquarium fish species.
Appearance
There are over 100 different types of koi fish, ranging from ancient varieties to modern blends of popular koi fish varieties. Colors, patterns, and general physical traits of koi fish vary greatly, but they’re always a mesmerizing presence in any aquarium.
Koi fish have maxillary barbels, two on each side of their mouths, which are taste bud-covered organs that they use to search for food in all water conditions by taking huge gulps.
Sexing koi fish is easy, as male koi fish have small pointy fins that are intensely colored and opaque, while females have round translucent fins.
Diet
Koi fish are omnivores, with an appetite that makes them some of the least picky aquarium fish you can keep. They will absolutely inhale any type of food, taking big gulps.
What’s on the menu for your pet koi fish?
- enriched pellets designed for koi fish (with plenty of minerals, vitamins, and nutrients);
- algae (lots of algae!);
- insect larvae;
- shrimp;
- lettuce;
- peas;
- watermelon;
- even people-food, like cereal or rice.
Although they might look intimidating to smaller fish when fully matured, koi fish will not eat other fish.
They will, however, vacuum up fish eggs off of a tank’s substrate or off of live plants.
It’s actually hard to keep koi fish in a planted aquarium, as their tendency to dig up substrate will up-root most live plants. Adding weeds or leaving them in charge of cleaning up algae overgrowth might distract them from your plants.
You should feed koi fish three times per day and avoid keeping them with other fish that they’ll have to compete for food with.
Breeding
Breeding koi fish can be a profitable business venture if you have the time and resources to do it right.
The upfront investment isn’t too costly, as juvenile domestic koi fish are relatively cheap to buy, but creating the ideal tank conditions for breeding koi fish can cost you a pretty penny.
Here are the steps you need to take to give a mating pair of koi fish the best chances to breed:
- Make sure your breeding pair of koi are well-fed during the month leading up to mating season;
- Late spring to early summer (May-June) is the ideal koi breeding “season”, following their natural life cycle;
- Choose healthy and strong koi fish to attempt breeding, as their genes will heavily influence how resilient and successful the resulting koi fish fry will be;
- Future koi parents should be in their prime when mating, between 3 to 6 years old;
- Domestic koi fish can mate even at the ripe age of 15;
- If you’re attempting to breed koi in an aquarium, they should be in a separate tank from all other fish;
- Koi fish eggs will sink to the bottom of the tank, so it’s helpful to have a spawning mat in place, so your koi pair can easily see their eggs;
- Keep the water temperature inside the tank between 65-70°F, during spawning;
- The male koi fish will seem like it’s harassing the female during the “mating ritual”, but he’ll actually push into her to help release the eggs, so he can fertilize them;
- A floating koi mesh cage/net can be useful once koi fry hatch, so they don’t become snacks for other fish or be sucked into the strong filter that a koi fish tank requires.
Tank mates
Koi fish can be hard to keep with other aquarium fish, not because of their temperament, but because they are significantly messier than most pet fish.
They constantly dig at the substrate, releasing debris and mucking up the water, making it harder for less hardy fish to share a tank with them.
Koi fish are otherwise peaceful and prefer to hang out with others of their own kind, with no drive to bother smaller fish.
The only truly incompatible fish species for your koi fish are those that they would have to compete with for food, and small fish from the Cyprinidae family, which can be intimidated and stressed by the large size of a mature koi.
| Ideal Tank Mates | Not Recommended |
| Goldfish | Bluegills |
| Larger Catfish | Rasboras |
| Killifish | Danios |
| Minnows | |
| Sunfish |
What diseases are koi fish at risk for?
Most disease-related koi fish deaths are caused by a virus called Koi herpesvirus, or KHV.
This is a highly contagious virus that hasn’t been reported in any other species, affecting only common carps (Cyprinus carpio) and koi fish.
KHV symptomatology is non-specific, but the most common signs a koi fish will display if carrying this disease are:
- white or gray lesions on the gills;
- skin hemorrhages;
- sunken eyes;
- obvious labored breathing.
Contracting KHV is fatal for koi fish, more often than not, and death usually occurs within 24-48 hours from the moment when symptoms start.
There isn’t an exact recorded way of preventing KHV from entering a koi fish tank/pond, but there are ways to prevent the virus from spreading rampantly in an aquarium and killing all your other koi fish:
- examine new koi fish before introducing them into your tank, looking for obvious signs of KHV infection;
- quarantine new koi fish for 2-4 weeks before introducing them to your other koi fish;
- remove koi fish that have KHV-specific symptomatology as soon as possible to prevent the virus from wiping out the entire koi fish population in your aquarium/pond.
Koi fish are also prone to developing ulcer diseases and fish lice infestations.
Popular Koi Fish Varieties
- Chagoi Koi
The Chagoi Koi is known as the most human-friendly variety of ornamental koi. This behavior has a lot to do with their greedy eating, almost fighting to be the first one being fed by a human owner. They’re the easiest koi fish to hand-feed, as they’re extremely food-driven.
- Ki Utsuri Koi
Ki Utsuri Koi is the rarest variety of ornamental carp, with glamorous color patterns of yellow and lacquer-black.
- Ghost Koi
Ghost Koi is one of the fastest-growing koi varieties. They’re a mix between Mirror Carps and metallic Ogon Koi. Their ghost-like color pattern makes them quite a sight to behold.
- Butterfly Koi Fish
The Butterfly Koi is one of the most common koi varieties in western aquariums. They are a mix of traditional Japanese Koi and long-finned carps. Their butterfly name comes from their long flowing fins and slender figures.
- Black and White Koi Fish
Black & White Koi, also known as Kikokuryu, have scaleless bodies, with a white color base and a black net pattern running along its single row of scales, followed by red, orange, or yellow patches of color.
- Japanese Koi Fish
Japanese Koi as a type of ornamental carp dates back to early 19th century Japan. The most colorful and unique wild-caught carp fish were caught and bred by rice farmers, creating a diverse gene pool that allows traditional Japanese Koi to outlive most koi fish varieties.
Conclusion
As amazing as the fact that some koi fish can live longer than their owners is, celebrating their 50th birthday in captivity, the responsibility that comes with owning a koi fish is even greater!
All you need to do to give your pet koi fish a long, healthy, and happy life is to meet its basic tank requirements and feed it a balanced diet to its heart’s content.
Koi fish are as stunning as they are big and will be the easiest to care for aquarium fish in its size category!
Recommended Reading
- How Big Do Koi Fish Get? Longevity, Care, And More
- How Long Do Mollies Live? Ideal Tank Conditions, Tank Mates, And Diet
- Why Do My Fish Keep Dying? 12 Common Causes
