Nisai, Sansai, Tosai: Understanding Koi Ages

Japanese Numbers Represent Koi Age

You may have heard these terms bandied about when discussing koi. Whether you’re looking to spruce up your home or business environment with these majestic fish, I want to help you understand more about them. Here’s what we’ll be taking a deeper dive into:

  • Fun and practical Koi terminology
  • Koi fish lifespan
  • What affects the price of Koi

Learn the Lingo

Becoming a koi aficionado means more than getting a pond and filling it with fish. You’ll need to brush up on your Japanese, so you can wow your friends and family with your newfound cultural knowledge.

Let’s start simple with how to identify your fish by its age. The popular terminology comes from variations of Japanese counters. Here are the words to use from ages 1-5:

  • Tosai
  • Nisai
  • Sansai
  • Yonsai
  • Gosai
Multi-colored koi fish

In the same fashion as your favorite beers, vendors divide koi into domestic and imported categories. Depending on their breeder’s location, the fish have different genetics. They also receive exposure to different food, water quality, and hibernation cycles.

Smaller koi in an outdoor concrete pond

Some varieties of koi contain references to their colors in their names. Here’s a convenient list for you. See if you can catch any while you’re shopping.

  • Sumi - Black
  • Shiro - White
  • Kin - Gold
  • Gin - Silver
  • Hikari - Metallic
  • Orenji - Orange
  • Aka - Red
  • Ki - Yellow

Don’t Koi Live to Be 1,000 Years Old?

Not quite. Though we might wish these wonderful fish could live forever, in reality, they have an average lifespan of 25-35 years. They also don’t grow forever to accommodate the size of their ponds. I’m sorry to be the one to rain on everyone’s parade.

This koi fish is mature - but hasn't been around for 1,000 years

It’s also worth knowing that Japanese koi tend to live much longer than “domestic” koi (roughly 40 years compared to 15.) I’ll bet you’re wondering what accounts for this difference.

Japanese breeders have rigorous quality standards they’ve maintained for generations. Consider that the highest quality koi wasn’t exported from Japan when they first hit the international market.

Japanese koi have different diets and genetics. Their breeders also ensure their maturation process occurs naturally, instead of forcing them to reach larger sizes prematurely.

Getting the Most Bang for Your Buck

Now that you’ve seen what makes Japanese koi special, you might be itching to buy one. Before you whip out your credit card, take a quick peek at a Koi Price Chart, it might make your head spin. At the high-end, koi fish sell for millions of dollars

Don’t get discouraged if you’re not ready to break the bank. Affordable options exist anywhere from the USA and Japan, to even Israel, China, or Indonesia.

Variances in color, age, sex, breeding, and size account for discrepancies in price. 

You’ll spend a significant chunk of change if you go after jumbo-sized koi or those with rare color patterns. 

Size and Age

The size of a koi fish impacts its price more than any other variable. Just like with any other animal, size increases with age, at least up to a point. 

Large Ogon koi fish

If you’re trying to go easy on your wallet, consider limiting your search to Tosai or Nisai koi. One word of caution, difficulty occurs when ascertaining the quality of a koi until it reaches maturation. I would steer clear of younger koi if you aspire to breed or enter your fish into a competition.

How Can I Tell My Koi Fish’s Age?

As a general rule, larger fish are older fish. Nevertheless, you have to be careful about using size as the sole determinant in gauging a koi’s age. 

Koi from different geographical regions have significant differences in breeds, genetics, environments, and diets. These changes all influence how fast koi mature.

Getting a precise age requires examining the fish’s ear bone. In practical terms, it’s best to stick with a rough estimate. You can obtain an age range by measuring your fish or checking with your supplier. The majority of koi online seem to sell in the one to five-year-old age range.

Frank Salvatore

In 2015 our family moved into a house south of Denver, Colorado with a  koi pond.  Since that time I've learned to really enjoy the koi fish and the pond. This blog is dedicated to providing helpful hints and information for koi pond hobbyists - as well as those of you who just inherited a koi pond and are thinking NOW WHAT?

About Me

Hey there - I'm Frank Salvatore. In 2015 our family moved into a house south of Denver, Colorado that had a Koi pond. The problem was I knew absolutely NOTHING about koi ponds.

This blog is dedicated to providing helpful hints and information for koi pond hobbyists - as well as those of you who just inherited a koi pond and are thinking NOW WHAT?
Learn More About Me

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