One of the most recognizable fish on the planet is the Koi fish (Cyprinus cardio), or Koi carp, as many like to call them. They are indeed a type of common carp, but they are ornamental by design.
The word Koi actually means carp in Japanese, and their natural habitat was Asia. So they sometimes go by the name Nishikigoi in Japan also.
Having been selectively bred, these fish have a variety of colors, patterns, scales, and even sizes on offer. The Japanese began to curate this species in the 19th Century, and now they are found the world over.
Chances are, if you know someone with a garden pond, they may have ventured into keeping a few Koi fish. And let’s make it clear here and now, these fish are not ideally suited to a tank setting. This is a fish tailor-made for a real pond in the great outdoors as they can grow to enormous sizes. Anything less would mostly do these fish a disservice. They can be kept in appropriately sized aquariums, but these will be huge, so they tend to be a less popular option.
Koi are also a species of fish that has an extensive lifespan, unlike many others in the hobby. Expect a firm commitment if you choose to have them or make provisional arrangements should your circumstances or living situation change just in case.
This fish can be obtained for a relatively inexpensive cost. But their popularity, alongside their many myths and legends in addition to special varieties, have introduced über expensive versions to the market too. We’re talking into the many thousands!
If the outdoor pond, lifespan, and care don’t faze you, read on to learn some of the key pointers of having these fish for a uniquely rewarding and relaxing hobby.
Koi History
How did these carp gain popularity in the first place? In the mountains of Japan, notably Niigata, there would be a large amount of snowfall which rendered the rice farmers isolated for months at a time.
They needed a reliable source of protein for those cold winter months and would keep Magoi in a ditch or unused rice paddy the rest of the year. Come the fall; the carp would be caught, salted, and stored for those isolated times. The farmers would be careful to keep a selection of juveniles in order to replenish the fish stock for the next season, and voilà, a healthy and self-sustaining protein source, was born.
It was important to keep the carp away from the rice, or they would have eaten the crop. But they did provide an excellent source of nutrients to the crop, so they had an additional use for the farmers in addition to being a food source. Fish waste water was ideal for fertilizing the crops.
Farmers then took notice of some of the carp having more patches of color than others and began to selectively breed the fish in their spare time as a hobby. The hobby spread, and koi keeping began to spread in Japan up until the 1960s, at which point it began to spread across the world with the advent of air travel.
Today there are enthusiastic Koi keeping clubs and shows, which is pretty impressive for a fish species that you can’t even keep in the house!
Koi Behavior
In general, Koi are peaceful fish even if they are related to Goldfish. They like to shoal, and a good size to aim for is 5 – 15 for a group of happy Koi.
They tend to occupy the lower and middle strata of the water column and are incredibly active swimmers. This will stress out less active fish, so you do need to keep them alongside other active and energetic species, but more on that later when we discuss Tank/Pond Compatibility.
You will see them pop to the surface of the pond or tank, too, though. If they didn’t, they wouldn’t be much fun to have in a pond if you rarely got the chance to see them!
How do Koi eat? They use their large, round mouths to scoop up sediment. They burrow their mouths into the sediment near plant roots and will take large gulps before filtering out mud and inedible content.
These fish are notorious jumpers, it should be noted. In a pond situation, if they should, they jump out; they usually wiggle their way back into the water. Not so in a tank setup, so ensure you have a secure hood on the tank.
Predation for pond fish remains an issue, so if you can, try to install protective fencing to keep your fish secure and out of harm’s way. Bird netting overhead can help against large birds of prey who will make a beeline for your vibrant and easily spotted Koi.
Koi Lifespan
If you cater to the needs of your Koi, your fish could expect them to live for anywhere from 30 – 50 years. The quality of their water will impact their lifespan, as always, so you can expect a longer life if you meet their requirements meticulously.
This is not a short amount of time to commit to.
We will discuss more on tank requirements a little later in this article.
Koi Appearance
When it comes to Koi Fish, there is a wide variety out there. The more highly prized color and pattern combinations will command the highest prices.
Color-wise you can find Koi in cream, red, blue, black, white, and yellow. The majority have a calico-type pattern and feature short rounded fins on their long, tubular bodies. Their scales are iridescent and highly reflective, making them easily visible below the water surface when observed from above.
Being a member of the carp family, they have barbels on their rounded snout on the sides and on their upper lip. Their mouth is completely toothless.
Typically they will Rach 2-3 feet in length (61 – 92 cm).
Here is a breakdown of some of the most popular varieties:
- Gold Koi Fish – usually featuring shades of orange, silver, and gold, this Koi variety can be called Ogon
- Butterfly Koi Fish – aka Dragon Koi as it has lengthier caudal and pectoral fins that drift gently as well as multicolored bodies making this a highly prized variety
- Black And White Koi Fish – aka Shiro Utsui this variety is exclusively black and white
- Taisho Sanke – aka Sanshoku this variety features three colors, including red, black, and white, with the most common being a white body with red patches
- Kohaku – native to Japan and consisting of a white body with red and orange patches, one of the most common varieties
- Shusui – this variety is scaleless with blue markings on the body
- Asagi – blue markings on the body and a net pattern on the top of the head
- Koromo – aka Koromo Koi Garomo this is a hybrid fish with a white base and then orange and red markings on the body with red scales
- Goshiki – available in black-blue, white, red, red-orange, and silver with net patterns on the body
- Kawarimono – a larger variety with a white body, red or black patches, and bluish or grayish scales
- Hikari Muji – one color only with a shiny metallic scale look
- Hikari Moyo – a metallic colored body and a more umbrella shaping to the body
Koi Habitat Requirements
Since these fish are native to ponds, streams, and lakes in Asia and now Europe, it is quite easy to replicate their habitat. We will take a look at the setup for housing them in an outdoor pond as this is the preferable way to keep these gentle giants.
Koi Pond Conditions
The ideal setup for these fish is something that has a natural look to it that avoids any pitfalls that can damage these fish.
Muddy pond bottoms will make these fish quite happy. Ideally, you would line your pond in concrete with a rubber lining and then add the substrate on top.
You will require a heater if your ambient temperatures fall below the 74ºF/23ºC mark day or night. It should never fall below that at any point during the year so ensure you have adequate heating and monitor this daily to ensure it is functioning properly.
As this is a pond setting, water flow is inconsequential and not required. If you decide for aesthetic reasons, you want a waterfall or some streamflow; this will not disturb your Koi as long as it isn’t too vigorous.
Filtration is still required, but you need to base its size and capacity based on 10 – 20% of the surface area of your pond. All traces of ammonia and nitrites need to be processed to keep your fish safe. Filtration is the single most expensive element when building a Koi pond and probably represents around 30% of the cost. Don’t skimp on this as it is key to having successful, healthy Koi!
Pond placement should be considered too, and some nearby tree shade is ideal to avoid overgrowth of algae and blooms due to too much light.
Non-invasive plants are ideal for planting and will help with the oxygenation of the water. Good options to include are:
- Floating Pondweed
- Water Lilies
- Duckweed
- Cattails
- Water Hyacinth
- Pickerels
Water conditions should be noted and maintained as follows:
- pH of 6.0 – 8.0
- Temperature between 74 – 86ºF (23 – 30ºC)
- Lighting conditions should be natural
Koi Pond Size
The minimum pond size for a single Koi would be 250 gallons, and for every additional one, you should add 250 more gallons.
Since we don’t advocate that you keep one solo and they enjoy schooling in a group of a minimum of four, you will really need a 1000 gallon pond for a minimum of four.
The pond needs to ideally be six feet deep minimum and have a variation in the depth with shallow and deep ends.
Choosing Pond Mates For Koi Carp
When it comes to finding species appropriate for your Koi Carp, you need to consider peaceful and active swimming species that won’t be aggressive or put off by their activity level.
Some excellent tank mate pairings for your Koi Fish that would work well include:
- Perch
- Puffer Fish
- Frogs
- Salamanders
- Grass Carp
- Bass
- Catfish
- Sunfish
- Goldfish
Skip adding snails and shrimp. Although they are brilliant at cleaning the tank and useful for the waste, your Orandas will create they will be gobbled up in no time by your Goldfish.
Avoid anything aggressive with your Koi as they are peaceful and are not into squabbling with other fish. Things like Oscar Fish, Rainbow Sharks, Silver Arowanas, and most Cichlids should be avoided if you want a harmonious pond or tank.
Koi Common Diseases and Illness
When it comes to diseases, Koi are susceptible to a herpes virus that affects all species of carp. Known as Koi Herpesvirus (KHV), it is usually fatal to the tune of 80%.
Symptoms to keep an eye out for include sunken eyes, lesions on the gills, and difficulty with respiration. It’s important to observe your fish on a daily basis and take notes for this reason.
Quarantining any additions to the pond is imperative for this reason alone. If one fish is detected with KHV, in many cases, the entire pond needs to be euthanized as it is so easily transmitted.
Are Koi A Good Idea For Your Tank?
Are Koi fish an option for you? We think they are superb for adding flair to any garden. Their relatively easygoing care needs make them wonderful to have.
With personality in spades and beautiful colors, Koi carp look spectacular and make for a rewarding experience for those who are apprehensive of taking on an in-house aquarium with the additional work and maintenance that goes into them.
A perennial favorite in the hobby, you are sure to enjoy these fish for many years, given their lifespan.
And if you happen to have a rice paddy, bonus!
