Understanding Sumi: Quality, Placement and Development

1. Why sumi deserves its own article

Sumi - the black pigment seen in varieties such as Sanke, Showa, Shiro Utsuri, Bekko and many Kawarimono - is one of the most dramatic and least predictable features in Nishikigoi. It can transform a young koi as it develops, strengthen or weaken an otherwise excellent pattern, and change the visual balance of the entire fish. Because black creates the strongest contrast against shiroji and beni, even a relatively small amount of sumi can dominate the eye.

The All Japan Nishikigoi Promotion Association (AJNPA) treats colour quality as part of the broader quality assessment and specifically describes good black as black, clear, uniform and lustrous when the koi is well finished. That simple description contains several ideas that beginners often collapse into one. Good sumi is not merely “a dark spot.” It has colour depth, surface quality, internal uniformity, clean integration with the surrounding skin, and an appropriate relationship with the variety and pattern.

Sumi also behaves differently from beni. Red pattern is often read as a comparatively stable structural element, while black can emerge, recede, consolidate, split, intensify or appear to sit beneath the skin for long periods. Some of this apparent movement is related to growth, skin thickness, scale development, physiology and the changing visibility of melanophores. Some is strongly genetic. This is why experienced buyers are careful about claiming that a particular grey shadow will definitely become a finished black plate.

2. Sumi terminology: a practical vocabulary

Japanese koi terminology contains a remarkably useful vocabulary for black pigment. Zen Nippon Airinkai (ZNA) distinguishes not only sumi itself, but also its quality, appearance and placement. These terms are best treated as descriptive tools rather than rigid laboratory categories.

3. What high-quality sumi looks like

High-quality sumi creates the impression of depth rather than surface staining. At its best, black looks dense, coherent and reflective - almost as though the pigment has substance beneath the skin. The visual comparison to lacquer is useful because lacquer is not simply dark; it combines depth, smoothness and shine.

A disciplined assessment separates several characteristics that are often confused:

• Blackness - how dark the pigment appears in neutral light. Good sumi should not read as brown, grey or dusty once it is meant to be finished.
• Lustre - whether the skin over the black reflects light cleanly. Deep colour without healthy lustre can still look flat.
• Uniformity - whether the plate is consistently black rather than strong in the centre and weak, mottled or peppered around the edges.
• Edge quality - whether the black meets surrounding shiroji or beni cleanly enough for the koi’s age and stage of development.
• Scale integration - on wagoi, whether the black sits coherently across the scale field rather than breaking into unrelated dark centres or pale gaps.
• Placement and proportion - whether the sumi improves the balance and identity of the variety rather than merely adding more black.
• Developmental appropriateness - whether the level of finish makes sense for the koi’s age and whether unfinished areas look orderly rather than degenerative.

These characteristics must be judged together. A perfectly positioned black spot that is weak, brownish and flat is not elite sumi. Conversely, extraordinary sumi quality can still be poorly placed and harm the visual composition. Quality and pattern are related, but they are not the same thing.

4. The biology behind black pigment

Black colour in fish is produced primarily by melanophores, pigment cells containing melanin-rich structures. Their appearance is not governed by a single factor. Genetics influences where black pigmentation can develop, while cell density, pigment production, skin structure, nervous and hormonal signalling, growth and environmental conditions influence how the colour is expressed and perceived.

Research on Japanese ornamental carp has found that melanocortin receptor 1 (MC1R) expression is higher during dark pigmentation development and in dark tissues, although particular MC1R alleles in that study were not directly associated with whether koi developed black. The important lesson is that koi pigmentation involves regulation and developmental timing, not a simple “black gene on / black gene off” model.

A separate study on Taisho Sanshoku examined melanophore responses to background colour and hormones. Ordinary common carp can lighten or darken substantially by changing how pigment granules are distributed inside chromatophores. The Taisho Sanshoku in the experiment showed much less fading and altered sensitivity to adrenaline and melanin-concentrating hormone. This helps explain why the visible black of koi is a living physiological trait rather than static paint.

5. Genetics strongly influence both the pattern type and the timetable

One of the most useful scientific findings for koi keepers is that different black-pattern systems do not necessarily share the same developmental pathway. A major inheritance study of koi distinguished the relatively small Bekko-type black pattern from the broad Utsuri-type pattern. Bekko crosses behaved in a way consistent with a dominant black-pattern effect, while Utsuri occurred only from Utsuri parents and at highly variable frequencies. The two pattern types were also associated with different early developmental timing.

For the hobbyist, this supports an observation breeders have made for generations: “sumi” is not one universal substance that behaves identically in every variety or bloodline. Sanke-style black, Showa/Utsuri-style black, Matsuba reticulation and the changing black of varieties such as Kumonryu should not be judged with one prediction rule.

Bloodline knowledge is therefore valuable when buying young koi. It does not allow certainty, but it gives context. Breeders who have followed generations of a line may know whether its sumi generally appears early, rises slowly, consolidates late, becomes strongly lacquered, or tends to finish at a particular body size. Those tendencies are far more useful than internet rules such as “grey always turns black.”

6. Blackness, depth and lustre are different things

Beginners often rank sumi only by darkness. Darkness matters, but a black patch can be very dark and still lack refinement. Under strong artificial lighting, a flat surface may photograph as almost pure black even though the skin has little living sheen. By contrast, high-grade sumi may show subtle reflections that make it appear less uniformly black in a photograph while looking extraordinary in person.

Depth is the impression that the pigment is integrated with excellent skin rather than sitting as a thin surface stain. Lustre is the reflective quality of the skin over the black. Uniformity is the absence of patchiness. These three qualities should reinforce one another. The best sumi is dark, deep, even and glossy at the same time.

When comparing koi, move the viewing angle. Strong sumi should remain convincing as light travels across the body. If a patch only looks black from one exact camera angle, examine whether you are seeing a lighting effect rather than true colour quality.

7. Hon-zumi, urushi-zumi and nabe-zumi

ZNA terminology is especially useful here. Hon-zumi refers to good dark sumi with thickness and lustre. Urushi-zumi describes the refined lacquer-like black especially admired in Taisho Sanke. Nabe-zumi refers to a browner, soot-like black with poor lustre. These terms train the eye to distinguish material quality rather than merely location.

Do not turn them into absolute colour swatches. Different bloodlines, skin types, ages and lighting conditions can make excellent sumi look slightly different. Use the vocabulary comparatively: does the black look polished or dusty, deep or superficial, cool and lacquered or brownish and dead? That comparative habit is more useful than trying to memorise one ideal shade from a screen.

8. Uniformity within a sumi plate

A sumi plate should be inspected internally, not only around its outline. Look for weak scale centres, grey islands, peppering, thin translucent edges and abrupt differences in darkness. On large koi, a broad black area that appears powerful from a distance may reveal uneven pigment at close range.

This is especially important on finished adults. A tosai may legitimately carry unfinished sumi, but a mature koi being presented as show-ready should show much greater coherence. Ask whether the unevenness looks like normal finishing, temporary condition or actual weakness. Video taken in neutral light is extremely helpful because it reveals texture and reflectivity that can disappear in a still photograph.

9. Tsubo-zumi and kasane-zumi: the ground underneath matters

Tsubo-zumi is black positioned on white skin. In Sanke, well-placed tsubo-zumi can be particularly striking because the clean shiroji isolates the black and allows its true quality to be seen. The shoulder is a classic location where an elegant tsubo-zumi accent can transform the balance of the koi.

Kasane-zumi lies over a beni plate. Because red pigment and black pigment visually overlap, the black can appear heavier or darker. In practical Sanke appreciation, sumi on white is often preferred when it creates cleaner contrast, but kasane-zumi is not automatically a defect. The real question is whether it contributes to the pattern and whether its quality and stability are convincing.

This distinction is also useful diagnostically. If you want to judge the true character of a koi’s sumi, study black that lies on shiroji whenever possible. It is less visually influenced by the underlying red and therefore gives you a cleaner view of colour quality.

10. Shita-zumi, kage-zumi and the danger of over-predicting hidden black

Young koi often show grey or bluish shadows beneath the skin that hobbyists call shita-zumi, kage-zumi, sinking sumi or similar terms. These areas are fascinating because they may indicate melanophore development below the visible surface. They are also one of the biggest sources of speculative buying.

Some hidden sumi does emerge and become important pattern. Some intensifies only partially. Some shifts in visibility as the koi grows. Some becomes less obvious. The scientific literature supports the idea that pigmentation is developmentally regulated, but it does not provide a reliable visual formula that lets a buyer predict the exact final shape of every shadow on an individual tosai.

Treat hidden sumi as evidence of possibility, not certainty. The more money the prediction is costing you, the more conservative your assumptions should become. A koi that is already excellent without the hidden sumi is a safer purchase than a mediocre koi that only becomes excellent in an imagined future.

11. Sanke sumi: refinement and strategic accents

Taisho Sanke is fundamentally read as a white-based koi carrying beni and black accents. The sumi should support the Kohaku-like red-and-white foundation rather than overwhelm it. Elegant placement, strong lacquer quality and good spacing are therefore especially important.

Classic Sanke sumi often appears as relatively discrete markings, frequently above the lateral line, with a clean head and lighter fin markings such as tejima rather than heavy Showa-style motoguro. These are tendencies, not a checklist that invalidates every exception. Modern bloodlines and individual patterns can vary widely.

The most important mistake to avoid is buying a weak Kohaku pattern simply because the young koi has exciting black. First judge the body, shiroji and beni framework. Then ask whether the existing and potential sumi elevates that framework. Sanke with too many scattered black dots can look busy; Sanke with one or two powerful, polished accents can look sophisticated.

12. Showa sumi: structure, wrapping and power

Showa uses black differently. Rather than reading as isolated decoration on a white-based fish, sumi is part of the structural architecture of the pattern. It may rise from lower on the body, wrap around the flanks, cross the head and interact strongly with the pectoral fins. This wrapping quality is one reason Showa can appear more powerful than Sanke.

Head sumi is acceptable and often desirable in Showa. Menware or hachiware - a strong black division through the head - can create dramatic character when balanced. Motoguro at the pectoral bases can visually anchor the front of the fish. Body sumi should contribute to three-colour balance rather than turn the koi into an indiscriminate dark mass.

Young Showa are notoriously difficult to predict because substantial sumi may remain beneath the skin. When buying tosai, judge the visible red-and-white framework and body quality first, then treat the hidden black as a development factor rather than a completed drawing. The breeder’s track record with that particular bloodline is unusually valuable in Showa selection.

13. Shiro Utsuri and other Utsurimono: black is half the design

In Shiro Utsuri, sumi is not a supporting accent; it is one of only two major colours. Weak, grey or muddy black therefore has nowhere to hide. Strong contrast between deep sumi and luminous shiroji is central to the variety’s impact.

Good Utsuri pattern typically has a wrapping quality rather than a series of detached spots. Head sumi and motoguro are part of the traditional visual language. Because the palette is simple, body conformation, skin quality and the refinement of the black-and-white boundary become even more exposed.

Hi Utsuri and Ki Utsuri require similar attention to sumi quality, but the interaction with the warm ground colour changes the visual contrast. Again, the black must be judged as material: depth, lustre, coherence and integration with the skin.

14. Motoguro, tejima and fin sumi

Fin markings can reveal both variety character and the quality of black pigment. Motoguro is concentrated sumi at the base of the pectoral fins, especially associated with Showa and Utsuri. Balanced motoguro can frame the shoulders and give the fish a powerful, anchored appearance. It should look deliberate and coherent, not like dirty pigment sprayed irregularly through the fin.

Tejima refers to black striping in the pectoral fins and is more typical of Sanke and Bekko. Fine, controlled striping can complement an elegant Sanke. Heavy black blocks at the pectoral bases would change the impression toward Showa-type character.

Never judge fin sumi without checking fin condition. A damaged, folded, inflamed or partially regenerated pectoral can distort the apparent marking. Structural health comes before aesthetic interpretation.

15. Menware and head sumi

Menware is the classic black head pattern that divides the face of Showa or Utsuri, often described as a lightning-like line from the mouth toward the shoulder. It can give a koi tremendous presence because the head is the visual starting point of the fish.

But menware is not valuable simply because it exists. Placement, balance and quality still matter. An overly heavy black head can obscure beni and shiroji, make the koi front-heavy or visually shorten the head. An elegant menware should work with the facial structure and the rest of the pattern rather than function as an isolated trophy feature.

16. Placement: good sumi does not mean more sumi

Pattern is the choreography of colour across the body. The same sumi plate can improve one koi and damage another depending on what lies before and after it. The eye wants rhythm: areas of activity separated by enough quiet skin to allow each colour to breathe.

On Sanke, one strong shoulder sumi and a few supporting accents may be enough. On Showa, black may need to connect more forcefully through the head, shoulders and flanks. On Shiro Utsuri, the black must share the body with white in a way that creates balance from nose to tail.

A useful exercise is to mentally remove each sumi marking. If removing one makes the koi look more balanced, that black may be technically high quality but compositionally harmful. If removing it makes the pattern collapse, the marking is doing structural work.

17. How sumi may change with age

There is no universal age chart for sumi. Genetics, bloodline, sex, growth rate, temperature, husbandry and individual development all matter. Nevertheless, age changes the question you should ask. On tosai, the issue is potential and organisation. On a mature show koi, the issue is whether the black is finished, coherent and supporting the total impression.

The table is a judging framework, not a biological timetable. Some bloodlines finish early; others are famous for late development. A late-developing fish can be valuable, but only when there is enough evidence in its overall quality and lineage to justify patience.

18. Growth can temporarily change how sumi is perceived

As a koi grows, scales enlarge, skin stretches across a greater surface and the body changes in volume. A sumi plate that looked compact on a 25 cm tosai may appear more open or uneven during rapid growth. Later, pigment can visually consolidate as the skin and scale field mature.

This is one reason snapshots can be misleading. Follow the same koi through repeated photographs taken under similar conditions. Development should be judged as a trend. Is the black becoming cleaner, deeper and better integrated with the growing frame, or is it breaking into weak islands and scattered specks? Longitudinal observation is far more informative than one exciting before-and-after image.

19. Sumi quality and sex: avoid automatic rules

Koi hobbyists sometimes attach fixed development rules to sex, such as assuming that one sex always finishes earlier or that another always produces superior black. Sex can influence growth, body shape, hormonal state and maturation, which may indirectly affect appearance, but the individual fish and bloodline remain more important than a simple male-versus-female rule.

When comparing young koi, use sex information as context rather than as a substitute for observation. A high-quality male with excellent skin and sumi is still high quality; a female does not automatically possess better future black simply because she is female.

20. Background colour and physiology can alter visible darkness

Fish pigment cells can redistribute pigment granules in response to nervous and hormonal signals. In many teleosts, background colour can produce rapid lightening or darkening. Research comparing common carp with Taisho Sanshoku found that Sanke showed much less skin fading in a white-background environment and reduced melanophore sensitivity to some regulatory signals.

The practical lesson is subtle. Koi colour is physiologically active, but ornamental strains have been selected for unusually persistent visible patterns. Do not assume that every short-term change is genetic failure, yet do not expect a pond-wall colour trick to manufacture high-quality sumi either. Genetics, skin quality and developmental state remain the foundation.

21. Temperature, season and condition

Many hobbyists report that sumi appears stronger in cooler periods and softer during warm, rapid-growth seasons. Seasonal physiology, skin condition, feeding intensity and growth can all change visual appearance. However, simple statements such as “cold water makes sumi” are too strong. Temperature does not draw a new genetic pattern onto the fish.

For tropical keepers, including those in Malaysia, the more important objective is stable, healthy husbandry. Warm water increases metabolic demand and reduces dissolved-oxygen capacity, so excellent aeration, filtration and sensible stocking become especially important. A healthy skin surface displays pigment more convincingly than a stressed fish regardless of theoretical colour conditioning.

22. Water quality, health and skin condition

Sumi is viewed through living skin. Excess mucus, parasite irritation, bacterial lesions, damaged scales, chronic ammonia or nitrite exposure, poor oxygenation and general stress can all reduce the clarity and lustre of the surface. Before diagnosing “weak sumi,” make sure you are not looking at weak condition.

Keep priorities in the correct order: health, stable water chemistry, oxygen, nutrition, growth management, then colour optimisation. Treatments marketed as direct sumi enhancers should be approached cautiously unless they are supported by evidence and safe husbandry principles. No additive can substitute for inherited pigment potential and healthy skin.

23. Lighting, bowls, cameras and the illusion of black

Black is especially vulnerable to photography tricks because cameras compress shadow detail. A phone may render a dark grey patch as solid black, while high-contrast editing can erase the texture that reveals weak sumi. Conversely, strong reflections on glossy black can make elite sumi look lighter in a still image than it does to the eye.

For remote buying, request unedited video in neutral daylight or evenly balanced lighting. Ask for the koi to swim and turn. Watch whether the black remains deep as the angle changes. Pause on the shoulder, dorsal line, tail section and pectoral bases. If possible, obtain both bowl footage and pond footage, because blue bowls can dramatically increase perceived contrast.

24. Variety-specific sumi priorities

25. How to evaluate sumi on a young koi

Young koi are where sumi prediction becomes most tempting. Use a repeatable sequence so excitement does not outrun evidence:

• Judge body conformation and general skin quality before looking for future black. Sumi cannot rescue a poor frame.
• Assess the quality of black that is already visible. Existing high-quality sumi is stronger evidence than a large area of vague grey.
• Study hidden or submerged areas for organisation. A coherent shadow is more interesting than random dirty speckling, but it is still only potential.
• Check whether the red-and-white pattern works even before the future sumi is imagined, especially in Sanke and Showa.
• Inspect the pectoral bases. In Showa and Utsuri, motoguro quality and symmetry can provide useful context.
• Compare siblings from the same breeder and age group. Relative differences are far easier to see than absolute predictions.
• Ask for breeder, parent line, age, sex if known, previous photographs and growth history. Development history is evidence; marketing adjectives are not.
• Price uncertainty honestly. The less finished the black, the more of the purchase is a developmental bet.

26. Signs that deserve caution

Unfinished sumi is not automatically weak sumi, but several features deserve closer inspection:

• Brownish or soot-like black that remains flat in neutral light on an otherwise well-conditioned koi.
• Large finished-looking plates that are internally patchy, with numerous pale islands or weak scale centres.
• Heavy jami or peppering that disrupts a variety expected to have cleaner organised sumi.
• An important black plate that is strong only where it overlaps beni but weak when it reaches shiroji.
• Motoguro that is badly imbalanced or sprayed diffusely through the pectoral fins rather than forming coherent bases.
• A pattern that only becomes attractive after mentally promoting every grey shadow into perfect future black.
• Photographs with crushed shadows, extreme contrast or obvious editing that prevent you from seeing pigment texture.
• Colour changes associated with injury, infection, scale loss or inflammation. Health should be diagnosed before aesthetic conclusions are made.

27. Common sumi myths

28. A practical 100-point sumi scorecard

This is not an official koi-show scoring formula. It is a training tool designed to force the eye to separate pigment quality from pattern excitement. Use the same scorecard repeatedly on different koi and, more importantly, on the same koi over time.

Do not use the total as a substitute for judgement. The exercise is valuable because it reveals why you like a koi. Two fish can receive the same total for completely different reasons - one may have finished black but ordinary placement, while another may have extraordinary placement and high-quality unfinished sumi. That distinction matters when deciding whether you want a show fish today or a development project.

29. A disciplined buying sequence for sumi

When evaluating a sumi-bearing koi for purchase, use the same order every time:

• First, assess health and body conformation.
• Second, assess general skin quality, shiroji and - where relevant - beni without letting the black dominate your attention.
• Third, evaluate the quality of the sumi that already exists: blackness, depth, lustre and uniformity.
• Fourth, evaluate placement and variety character: Sanke accent, Showa structure, Utsuri balance, Bekko refinement.
• Fifth, inspect hidden or unfinished areas and classify them as probability, not certainty.
• Sixth, add developmental context: breeder, bloodline, siblings, age, past photographs, growth history and current condition.
• Finally, decide how much of the purchase price is for quality already present and how much is for a future scenario.

This sequence prevents a common auction mistake: falling in love with a dramatic future pattern that exists mainly in the buyer’s imagination. The highest-potential koi are usually compelling even before every future detail has finished.

Frequently asked questions

Is the blackest sumi always the best? No. Deep black is important, but lustre, uniformity, skin quality and placement also matter. A flat black patch can be darker than a glossy patch in a photograph yet less refined in person.

What is shita-zumi? It is hobby terminology for black pigment or shadow that appears to sit beneath the visible surface. It may rise and consolidate, but not every submerged area becomes finished black.

Why is tsubo-zumi valued in Sanke? Because black placed on shiroji can show its quality clearly and creates strong clean contrast. It can also provide elegant punctuation to the red-and-white pattern.

Is kasane-zumi bad? No. Kasane-zumi is black over a beni plate. It can be attractive and useful, although tsubo-zumi often gives a cleaner view of true black quality.

Should Sanke have black on the head? Traditionally Sanke is appreciated with a clean head and black mainly on the body. Minor exceptions exist, but heavy head sumi changes the classic Sanke impression.

Should Showa have sumi on the head? Head sumi is normal and often desirable in Showa. Menware can be a powerful feature when it is balanced and high quality.

Does motoguro guarantee good body sumi? No. Balanced motoguro can indicate strong variety character and good fin pigment, but it does not provide a precise map of how every body plate will develop.

Can water hardness make sumi come up? Water chemistry affects overall physiology and skin condition, but there is no reliable evidence that one hardness value can be used as a universal switch for creating a desired sumi pattern.

Why does my koi look blacker in winter? Season, growth, skin condition, lighting and physiology can change visible colour. A seasonal change does not necessarily mean the underlying genetic pattern has changed.

How should I buy an unfinished Showa? Buy the body, skin and red/white framework first; assess the quality of visible sumi; then use hidden black and bloodline history as evidence of possibility rather than certainty.

Can finished sumi disappear? Black can change with growth, condition and physiology, and some patterns are more stable than others. Injury or scale loss can also alter appearance. Persistent structural pigment loss should not be assumed to return.

What is more important: sumi quality or sumi placement? Both matter, but they answer different questions. Quality tells you how good the black material is; placement tells you whether that material improves the composition. Elite koi need both in appropriate balance.

Conclusion: read sumi as quality, architecture and time

Sumi becomes easier to understand when you stop asking only, “Will this black come up?” and start asking three separate questions: “How good is the black material?”, “What does its placement do to the pattern?”, and “What evidence supports the development I am expecting?” Those questions separate observation from speculation.

In Sanke, the best sumi can behave like elegant punctuation. In Showa, it can form the architecture of the design. In Utsuri, it is half the visual identity of the fish. Across all of them, truly high-quality sumi combines blackness, depth, uniformity and lustre with skin quality and variety-appropriate placement.

The best way to learn is longitudinally. Follow individual koi from tosai through nisai, sansai and adulthood. Compare photographs taken in similar conditions. Note which grey areas rose, which disappeared, how motoguro changed, how body growth altered balance, and how finished black behaved on white versus red. Pattern prediction improves not from memorising slogans, but from accumulating real development histories.

The next article in this series, KD-006, will continue the quality-and-development framework by examining the next core visual component in the established KD sequence.