Thinking About Koi Fish? (You Must Read This First!)

I can’t blame anyone who has admired a pond full of beautiful koi fish and considered getting their own. What’s not to admire? Koi fishes are hardy, gregarious, brightly colored, and can reach up to 3 feet (90 cm) in length. The Koi fish is also popular for their variety of colors, and their decorative use in outdoor ponds.

But before you grab a shovel and start digging a hole in your yard, there are some things you should know first!

Time & Money Commitment

First and foremost, you need to know that keeping koi fish requires a certain level of commitment. This involves time and money.

How long does a Koi fish live?

Beautiful koi fish at a pondAre you the type of person that goes to the pet store and buys a pet on a whim? Do you find that you become uninterested or bored with your pet after the initial excitement wears off? If so, koi fish are not for you.

Koi are a long-lived fish. How long? Koi fish live 25-35 years on average, with the oldest known koi living to a reported 226 years! This is far longer than your dog or cat will live.

Are you prepared to care for these fish for that long? If you do need to part with your koi will you put in the effort to make sure they go to a fantastic home?

The lifespan of these amazing fish is something that needs to be considered before taking the plunge.

How much are koi fish?

Once you have accepted the fact that koi fish is a long term commitment, you need to consider the financial cost.

There are many different koi fish available in terms of quality of stock and variety. Juvenile water garden quality koi can sell for as little as $10 apiece and show quality koi can sell for many thousands and thousands of dollars.

There is, of course, a middle ground where quality koi can be had for mere hundreds of dollars apiece. A simple web search for “koi for sale” will bring up many quality breeders that ship koi via mail.

Beyond the cost of the fish themselves is the cost of the pond. The price can vary depending upon the pond and how much work you are willing to do yourself.

Having a koi pond professionally installed can cost $5,000 – $20,000 on average, with the sky being the ultimate limit if you want to go above and beyond. This can be done cheaper if you are able to do some of the work on your own. Make sure you research first so that you understand koi pond design and the work required.

Different Varieties of Koi Fish

Different type of Koi Fish

There are many different types of koi fish that you can find these days. Keeping up with the different varieties of fish koi can be quite a challenge. Here’s a list of the top Japanese koi fish varieties down below:

  • Kohaku
  • Taisho Sanke
  • Showa Sanshoku
  • Tancho
  • Shiro Utsuri
  • Hi Utsuri
  • Ki Utsuri
  • Asagi
  • Shusui
  • Matsuba
  • Platinum Ogon
  • Yamabuki Ogon
  • Kujaku
  • Hariwake
  • Kikusui
  • Kumonryu
  • Beni Kumonryu
  • Chagoi
  • Soragoi
  • Ochiba Shigure
  • Goromo
  • Goshiki
  • Kikokuryu
  • Kin Kikokuryu

These are by far the most famous Japanese Koi Fish available from different farmers in Japan. They come in different color varieties, including black, red, yellow, blue, and white combinations. The pattern will determine the type of koi, and they usually combine two or three different colors. Also, some patterns will have a unique resemblance like the Tancho. The breeder can provide more information in detail before you order.

Everything a Koi Needs

A school of koi fish has all of the same needs as other pet fish, just on a much larger scale. But, there are also some other considerations unique to an outdoor water garden you will have to be aware of.

Feeding Koi

With koi being such a hardy fish, it can be easy to take their health and wellbeing for granted.

Do you want to feed your koi the cheapest feed available or buy the best koi food available that will enhance their color, growth, and health? Some research should be done as not all koi food is created equal. Things such as protein content, micronutrients, and color enhancers are important to know and understand.

Moreover, a koi’s diet should vary seasonally. During the summer, you should be feeding multiple times a day, and during the coldest winter months, they shouldn’t be fed at all.
Care should also be taken to avoid overfeeding a koi. This can lead to health issues as well as a build-up of uneaten food in the pond that can spike ammonia and nitrate levels.


As previously discussed, your koi will need a water garden. Being a large fast-growing fish there aren’t really any commercially available fish tanks for a school of koi. There are some koi enthusiasts who have built custom indoor aquariums for koi, but they are the exception.

For example, a 12-inch koi needs at least 100 gallons of water. If you have a small school of 5 koi, that would mean you need a 500-gallon aquarium. The alternative to an aquarium this large would be an indoor pond, but this is impractical for most people. Thus, the only time I would recommend keeping koi in an aquarium is while they are still small.

Koi Pond Size

So how big does our koi pond need to be exactly? 1,000 gallons is generally accepted as the minimum amount of water needed in a koi pond. How big is this? An 8 foot long, 6 foot wide and 4-foot deep pond with decor would hold about 1,200 gallons. I want to reiterate, this is the minimum, and you should plan for larger if possible.

In addition to this minimum size, the pond also needs to be at least 3 feet deep. In climates with more extreme temperatures, 4 feet is needed. This isn’t just needed for protection from extreme temperatures but also to provide cover from predators.

If this is the minimum, what is the ideal size? The ideal size is 25 feet long by 13 feet wide and 3 feet deep. This gives you enough room for 15-20 happy koi fish.

Water Quality

As with any fish, water quality is important to koi. While they are known as hardy fish, this does not mean that they can or should be kept in dirty water. The Japanese Koi Fish responds better to freshwater according to history. They love swimming in it, and their color can also be more distinctive.

The primary way to keep the water clean is with a water filter. With a larger volume of water to process, you will need a heavy-duty filtration system. If you created a small pond, you might be able to get away with a simple stand-alone filter. But, if you have a larger pond and water clarity is a priority, be prepared to install a much more complex system.

Professional koi pond filtration systems can be complex and expensive. They can involve multiple drains and outlets, water pumps, various types of filters, water features, and complex plumbing. The serious DIY’er can pull this off on their own, but everyone else should seek the help of a professional.

Pond Maintenance

Freshwater pond full of koi fishThe national average cost for professional koi pond maintenance is $2,000 a year. This cost will vary with pond size and your location. Whether you hire a koi professional or not, there are certain things that you will need to ensure are done on a regular basis.

Daily maintenance involves simple things like cleaning out leaves, uneaten food, or other debris. Allowing this material to accumulate in your pond will not only make it look unsightly but will also negatively affect your water quality.

On roughly a weekly basis, a partial water change of approximately 10 percent should occur. Make sure to dechlorinate your tap water before you add it back in. This is also a fantastic time to test your water chemistry, check your filters, and clean out anything else missed during your daily cleanings.

Springtime deep cleaning involves the bulk of the maintenance you will have to perform on your koi pond. This involves removing your fish and completely draining and cleaning your pond. All pond equipment such as water features, filters, and pumps will need to be thoroughly inspected and cleaned.

Trimming and pruning of any water plants will also need to be done on a seasonal basis. You should try to keep every Japanese koi in clean water no matter what part of the world you live in.

Koi Health

With the level of investment, koi require, it pays to pay close attention to the health of your fish. In order to spot problems early, you will need to spend time watching your koi in order to become familiar with their behavior.

Pay attention to how they swim, how much energy they have, their social behavior, and their feeding habits. If they start behaving erratically, acting sluggish, not eating, or are isolated from the group, you may have a problem.

  • Symptoms of Illness
  • Ragged or torn fins
  • White spots
  • Sitting at the bottom of the pond
  • Gasping at the water’s surface
  • Lack of appetite
  • Fins clamped close to the body
  • Red sores
  • Self isolation from other fish

Various illnesses can affect your koi and include common diseases such as Ich, Columnaris, Carp Pox, Anchor Worms, Chilodonella, and Aeromonas. These can be caused or promoted by events such as a drastic change in the water temperature, failure to quarantine new fish, poor water quality, and predator attacks.

The specific illness they are infected with will determine the type of treatment necessary. Common treatment techniques include things such as adding salt to the water, doing water changes, and treating with medications. Other things like dropsy are essentially lethal by the time symptoms are identified, and the affected fish should be immediately removed.

With such a large financial investment, it is sometimes best to consult a qualified veterinarian if a health issue arises.

Final Thoughts

The Japanese Koi Fish should be kept in freshwater. Many of the koi patterns will sell for a high price, and they are usually imported from Japan. When you order in bulk quantities, you will receive different varieties in color.

I hope this has helped you get a grasp on all of the considerations and things involved with owning koi. There is a significant time & money investment for the koi owner, and I simply want to educate those interested. If you do choose to pursue this amazing hobby, I give you my congrats and wish you the best of luck!

Last Updated on 26/08/2020 by Karen Snow

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