Miyuki Medaka (幹之メダカ – Miyuki)

A luminous icon of the medaka world

Overview

The Miyuki Medaka (幹之メダカ) is one of the most iconic ornamental rice fish strains, celebrated for its dorsal iridescence known as taigaikō (体外光). This beautiful shimmering effect along the back revolutionized medaka breeding and continues to inspire countless new varieties.

Origin and History

• Year Developed: 2007
• Breeder: Takashi Suga (Japan)

In 2007, breeder Takashi Suga discovered a medaka with a faint blue-white glow along its back. By 2008, he succeeded in stabilizing this unique expression, and the result was the birth of the Miyuki Medaka. It was officially unveiled at the 1st Japan Medaka Exhibition, instantly gaining popularity and setting a new benchmark for ornamental medaka.

Key Features

• Dorsal Iridescence (体外光): The signature feature — a glowing stripe along the top of the body.
• Body Color Variations:
  • Standard Blue Miyuki
  • White Miyuki (白幹之)
  • Yellow/Amber Miyuki (Akari / 灯)
  • Sunset Miyuki (サンセット幹之) with warm gradient tones
• Body Types:
  • Standard body
  • Daruma type (ダルマ幹之): A short, rounded body with the same dorsal glow — compact and adorable

Miyuki Medaka Light Grading System (体外光の等級分類)

A closer look at how dorsal shine is classified in Miyuki Medaka

As of 2015, the Miyuki Medaka’s (幹之メダカ) signature dorsal iridescence — known as taigaikō (体外光) — began to be formally categorized based on the length of the light extending from the base of the dorsal area. These categories are widely recognized and used by breeders to classify the visual intensity and quality of the fish.

Here is the breakdown:

Light Grade Categories (Based on Shine Length)

• Weak Light (弱光)
  Shine reaches up to 1/4 of the body length
  → Subtle shimmer, often seen in earlier-stage or lower-grade individuals

• Strong Light (強光)
  Shine extends to around half the body length
  → Noticeably glowing stripe but not full coverage

• Super Light (スーパー光)
  Shine reaches up to the base of the pectoral fins
  → Full-length dorsal glow — a popular and highly prized appearance

• Strong Super Light (強スーパー光)
  Shine extends to the eye region
  → Deep, vivid shine that pushes beyond the back and toward the head

• Extreme Light (極光)
  Shine extends all the way to the tip of the mouth
  → The highest classification — extremely rare and visually striking

Note:
The classification is based on the end point of the iridescence, starting from the base of the back. The start point is assumed and not described in each level.

Influence on Other Strains

Miyuki Medaka has become a foundational strain in modern medaka breeding. Many popular varieties — including those with long fins, lamé scales, or swallow traits — trace their iridescent features back to Miyuki lineage.

Conclusion

The Miyuki Medaka isn’t just a beautiful fish — it’s a piece of medaka history. With its dazzling dorsal glow and timeless aesthetic, it remains one of the most beloved and influential varieties among breeders worldwide. Whether kept in a pond, bowl, or tank, this radiant strain never fails to impress.

Image and translation courtesy of: https://medakazukan.net/0100_miyukihikari/