Shinkai (Deep Sea) Medaka (深海メダカ)

Physical Characteristics

The Shinkai Medaka, also known as the Deep Sea Medaka, is a uniquely refined strain recognized for its clear, glowing blue body and a rare internal feature known as the blue peritoneum (腹膜青 / fukumaku ao). Unlike other medaka with strong pigmentation, the Shinkai appears delicate and almost ethereal, with minimal black pigment and a translucent, cool-toned look.

• Body Color: Transparent to pale blue, with a luminous clarity
• Unique Trait: Blue peritoneum — the inner abdominal wall appears blue
• Scales: Minimal black pigment, creating a clean and peaceful aesthetic

Breeding and Development

The Shinkai Medaka was developed in 2010 by Japanese breeder Ryusei Nagaoka (長岡龍聖). It was selectively bred from Blue Miyuki (青幹之) strains that showed a blue-tinted peritoneum. Through careful refinement, breeders eliminated external shine, reduced black pigmentation, and stabilized the rare blue peritoneum trait.

While its name may evoke the deep sea, the fish’s clarity and lightness offer an elegant contrast to more intense varieties.

• Strain Name (品種名): Shinkai (Deep Sea)
• Breeder (作出者): Ryusei Nagaoka (長岡龍聖)
• Released: 2010
• Key Trait: Blue peritoneum (fukumaku ao)
• Lineage: Derived from Blue Miyuki with selective reduction of external shine and pigmentation

Care and Maintenance

To fully appreciate the subtle beauty of the Shinkai Medaka, environmental conditions are key:

• Lighting: Provide ample sunlight or LED lighting to enhance its translucent blue appearance
• Tub or Tank Color:
  ➤ Use white or light-colored containers — this helps the fish stand out and allows the clarity of the body to shine through
  ➤ Avoid black tubs, as the fish may become visually lost due to their low pigmentation
• Water Quality: Clean, stable water supports both health and visual clarity
• Diet: A well-balanced diet enhances natural coloration and overall condition

Conclusion

The Shinkai Medaka is a serene and minimalist beauty that stands out for its crystal-clear blue tone and rare blue peritoneum. Created through thoughtful and intentional breeding, this strain remains a favorite among medaka enthusiasts who value subtlety, purity, and elegant design in their aquatic collections.

Image and translation courtesy of: https://medakazukan.net/0117_sinkai/

🌊 A captivating strain with a glowing blue color that feels like you’re gazing into the ocean depths. Best viewed from above in a white container!