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Koi grading and quality

By the koi.wiki editorial team · Updated

Key facts: Koi grading is the process of evaluating body shape, skin quality, finish and pattern to separate pond-quality koi from show-quality koi, and to identify tategoi — young koi judged to have the potential to improve with age.[1][2]
The All Japan Nishikigoi Promotion Association (JNPA) states that nishikigoi are generally evaluated on four criteria: body shape, quality, finish and pattern[1], while its general Q&A on koi shows summarizes judging as resting on three main criteria — body shape, quality and pattern — with body shape particularly emphasized[3]. Commercial sources describe a simpler commercial split between “pond quality” and “show quality” koi, with show-quality fish possessing stronger body conformation, cleaner quality and more attractive patterns, according to the US dealer Kodama Koi Farm[2].Grading in the broader ornamental fish trade is also a practical farm process. The University of Florida IFAS Extension describes grading as a time-consuming visual inspection for characteristics such as size, color, fin development, and health indicators including scale loss, torn fin rays, eye damage and parasite load, performed mechanically, by hand, or both[6].

Body shape and conformation

Zen Nippon Airinkai (ZNA) terminology describes several anatomical reference points used when assessing body shape, including ozutsu, the caudal peduncle between the end of the dorsal fin and the base of the tail, whose thickness is described as a criterion for predicting future body conformation[7]. Other terms include taikei or karada (body conformation/shape) and taiku, described as physical constitution or build, referring to a firm, strong bone structure rather than a soft, tender body[7].According to the dealer Kodama Koi Farm, good body conformation in competition koi includes a smooth, torpedo-like shape, fins proportioned to body size, a clean and appropriately sized head and mouth, a strong tail tube said to indicate good genetics and growth potential, left-right symmetry without deformities, and graceful swimming movement, with erratic movement suggesting possible health issues[4]. A comparison of Gosanke varieties by the same dealer associates Kohaku with a strong, torpedo-like body, Sanke with a sleek, well-balanced form, and Showa with a thick, powerful appearance[8]. See also koi anatomy and how koi varieties are classified.

Skin quality and finish

The JNPA associates quality with thick, clear red, truly black ink, and clean white skin, with uniformity and clarity of each color raising evaluation[1]. Kodama Koi Farm describes high-quality koi as having lustrous, almost translucent skin, which it calls essential for varieties such as Kohaku[4]. The same dealer lists shiroji (the purity of the white base) as a key factor in pattern quality, describing it as a clean, bright, unblemished canvas that enhances contrast with other colors[4].Kodama Koi Farm also describes kiwa, the sharp, clean edge at the boundary of a color marking, and sashi, the slightly blurred leading edge of a pattern that should remain parallel to the kiwa and extend no more than about one scale width, as indicators used in judging the Gosanke varieties (Kohaku, Sanke and Showa)[4]. Scale type also affects the visual lustre of skin: the American Koi Judges Association glossary defines fukurin as the area of skin around the smaller scales of good metallic koi, noting that the smaller the scales, the greater the lustre, a factor relevant to Kinginrin (Ginrin) koi[5].

Pattern

Pattern is described by the JNPA as partly a matter of personal preference, though for red-and-white koi, round dots and three- or four-step patterns are often favored, and for Sanke, shoulder ink (kata zumi) is often preferred[1][5]. Kodama Koi Farm identifies symmetry, color depth, pattern flow (how the design complements body shape), and shiroji purity as the main factors determining pattern quality[4].Specific pattern terms are used to describe how markings are arranged. A maruten pattern places a separate red marking on the head apart from body markings, prized for symmetry and for drawing attention to the head, according to Kodama Koi Farm[4]. A tancho pattern, by contrast, is a red marking confined to the head with no other red on the body, according to the American Koi Judges Association[5]; see Tancho. Step patterns — described as yondan (four-step) and similar terms — refer to the number of distinct red markings along the body; a dealer source notes that four-step and especially five-step Kohaku patterns are considered rare compared with common one-, two- and three-step patterns[9][5].

Show quality versus pond quality

According to Kodama Koi Farm, koi are commonly classified commercially into pond-quality and show-quality categories, with the distinction resting on beauty: show-quality koi have strong body conformation, excellent quality, and attractive patterns that make them ready to compete or capable of developing competition potential, while pond-quality koi, regardless of bloodline, are considered beautiful but do not meet strict competition criteria[2]. The dealer states that Kohaku, Sanke and Showa are the most popular show varieties because they most often win Grand Champion titles[2]; see Kohaku, Sanke and Showa.The same dealer lists bloodline, beauty (body shape, quality and pattern), variety and rarity as primary determinants of koi value, along with size and age, noting that larger and older adult koi (two to four years) tend to fetch higher prices than smaller, younger fish[2]. A separate dealer source on rarity lists bloodline importance, pattern balance, skin quality, body structure and show history as evaluation factors tied to championship value[9]. For more on cost factors, see how much do koi cost? and for age terminology see age terms: tosai, nisai, sansai and yonsai.

Tategoi and future potential

Tategoi is defined by the American Koi Judges Association as a koi that a breeder keeps because it is believed it will improve and become more valuable at a later age, and the glossary calls it “the most misused word in the koi language”[5]. The same source notes that historically dealers could not buy these koi, but due to demand, breeders began selling some tategoi in early spring, and that they do not come cheap[5]. Once a breeder decides to sell a koi, it is called tateshita rather than tategoi[5].Kodama Koi Farm similarly describes tategoi as koi of any age judged to have great potential, contrasted with tosai, which refers simply to one-year-old koi[2]. The same dealer notes that Gosanke varieties can change considerably with age, with young koi often showing incomplete sumi development — particularly in Showa — and black deepening while red becomes richer as the koi matures, meaning evaluation of potential requires understanding how colors and patterns evolve over time[8]. See fry rearing and culling (senbetsu) for related selection practices at the breeding stage.

Grading as a farm process

Outside of show judging, “grading” also refers to the routine farm process of sorting fish. The University of Florida IFAS Extension explains that ornamental fish are commonly graded first by size — mechanically or by hand — and then by hand for color and other quality traits, with careful handling important to minimize stress[6]. Hand grading allows close inspection of traits but is more time-consuming, while mechanical grading handles large numbers of fish quickly but can be rougher on sensitive fish[6].Culling — removing fish that do not meet desired traits — is described as helping maintain favorable characteristics in a population and preventing stunted growth or poor quality over successive generations[6]. The Southern Regional Aquaculture Center notes that selective grading devices can reduce handling time and stress during sorting and harvest, and that stable water quality and oxygen levels should be maintained throughout handling to reduce stress-related harm to fish[10]. For koi-specific culling during fry rearing, see fry rearing and culling (senbetsu).

Common questions

What is the difference between show-quality and pond-quality koi?
According to the dealer Kodama Koi Farm, show-quality koi have strong body conformation, excellent quality, and attractive patterns that give them competition potential, while pond-quality koi are considered beautiful but do not meet strict competition criteria[2].
What are the main criteria used to judge koi?
The All Japan Nishikigoi Promotion Association describes four general criteria — body shape, quality, finish and pattern — with body shape considered most important, especially in larger koi[1]. Its general Q&A summarizes judging under three criteria: body shape, quality and pattern[3].
What does tategoi mean?
Tategoi refers to a koi kept by a breeder because it is judged likely to improve and increase in value with age; once sold, it is called tateshita rather than tategoi, according to the American Koi Judges Association glossary[5].
What does shiroji mean in koi grading?
Shiroji refers to the purity of a koi’s white base color, which serves as the background for red and black markings; a clean, bright, unblemished shiroji is considered a sign of pattern quality by the dealer Kodama Koi Farm[4].
Why are Kohaku, Sanke and Showa the most common show varieties?
According to Kodama Koi Farm, these three varieties, collectively called Gosanke, are the most popular show koi because they most often win Grand Champion titles at competitions[2].

References

  1. ^ Examination criteria - All Japan Nishikigoi Promotion Association. All Japan Nishikigoi Promotion Association. jnpa.info/en/show/examination/. Retrieved November 2026.
  2. ^ How Much Do Koi Fish Cost? Koi Pricing Guide for USA. Kodama Koi Farm (koi dealer). kodamakoifarm.com/how-much-do-koi-fish-cost/. Retrieved November 2026.
  3. ^ Q&A - All Japan Nishikigoi Promotion Association. All Japan Nishikigoi Promotion Association. jnpa.info/en/qa/. Retrieved November 2026.
  4. ^ Koi Patterns and Markings: A Guide to Their Meaning, Types, and Selection. Kodama Koi Farm (koi dealer). kodamakoifarm.com/koi-patterns-and-markings/. Retrieved November 2026.
  5. ^ Glossary – American Koi Judges Association (AKJA). American Koi Judges Association. akjajudges.com/glossary/. Retrieved November 2026.
  6. ^ UF/IFAS EDIS FA118: Grading Ornamental Fish. University of Florida IFAS Extension (EDIS). ask.ifas.ufl.edu/publication/FA118. Retrieved November 2026.
  7. ^ NISHIKIGOI TERMINOLOGY 1 BODY | Zen Nippon Airinkai. Zen Nippon Airinkai. zna.jp/en/keep-nishikigoi/nishikigoi-terminology/nishikigoi-termino…. Retrieved November 2026.
  8. ^ All About Gosanke Koi Fish Varieties "The Big Three!". Kodama Koi Farm (koi dealer). kodamakoifarm.com/gosanke-koi-fish/. Retrieved November 2026.
  9. ^ Which Koi is the Rarest: How Can I Judge Superiority?. Kodama Koi Farm (koi dealer). kodamakoifarm.com/rarest-koi-fish/. Retrieved November 2026.
  10. ^ SRAC Publication No. 474: The Role of Stress in Fish Disease. Southern Regional Aquaculture Center. srac.msstate.edu/pdfs/Fact%20Sheets/474%20The%20Role%20of%20Stress%…. Retrieved November 2026.