Shusui Koi
Shusui is the Asagi undressed - a scaleless (doitsu) koi keeping only a single row of large mirror scales along the dorsal line, sky-blue skin beneath and red blazing up the flanks.
🗓️ Last reviewed: July 2026
Overview
Shusui is the Asagi undressed - a scaleless (doitsu) koi keeping only a single row of large mirror scales along the dorsal line, sky-blue skin beneath and red blazing up the flanks. The smooth skin makes its colours glow like enamel, and the neat dorsal scale row gives it a tailored, architectural elegance.
Natural History
Created in 1910 by crossing Asagi with German mirror carp (imported for scale-less food fish); one of the first and most enduring doitsu varieties.
Appearance
Smooth blue back split by one dorsal row of large dark scales, red from belly to mid-side (or higher in Hi Shusui); clear head prized. To 60-90 cm.
Tank Size & Setup
Koi-standard pond; smooth skin shows sunburn and knocks more than scaled fish - shade and smooth edges help.
Water Parameters
Standard koi seasonal care; skin quality is water quality made visible.
Diet
Seasonal feeding; the enamel skin rewards clean diets and clean ponds.
Health & Lifespan
Average lifespan is 25-40 years. Koi-standard lifespan; doitsu skin is slightly more injury-and-sun sensitive - minor, manageable.
Pros & Cons
Pros
- Enamel-bright blue unique in ponds
- Tailored dorsal scale line
- Asagi heritage, modern look
- Glows in overhead view
Cons
- Skin shows every scratch
- Sunburn possible in shadeless ponds
- Dorsal row must be tidy - genetics vary
- Subtler than Gosanke brights
Shusui Koi - frequently asked questions
What does 'doitsu' mean?
'German' - referring to the mirror-carp scale-reduction genes bred in from German food carp. Doitsu versions exist across many koi varieties.
Shusui or Asagi?
Texture choice: Asagi's woven scale-net vs Shusui's smooth enamel and single tailored row. Ponds with both display the palette twice.
What's a Hi Shusui?
A version where red rises over the back, flooding most of the blue - louder, popular, equally hardy.
🧠 Test yourself: guess the fish
Three clues from our quiz bank, each about another of our fish. Can you name them?
Clue 1.Sporting two pairs of whiskers, this bottom-dweller is happiest kept in groups as it constantly sifts the substrate for food.
It's the Corydoras Catfish - read the full profile →
Clue 2.This tiny, hardy aquarium fish gives birth to live young rather than laying eggs, earning it the nickname 'rainbow fish.'
It's the Guppy - read the full profile →
Clue 3.Contrary to popular myth, this hardy pet has a memory spanning months and should never be kept in a tiny bowl.
It's the Goldfish - read the full profile →