Izumo Nankin Care Guide | Japan's National Treasure Goldfish from Shimane Prefecture
Explore the characteristics, history, and care methods of the Izumo Nankin, Shimane Prefecture's traditional goldfish designated as Japan's natural monument. Discover its distinctive compact body shape and beautiful four-lobed tail, how to select traditional vessels and tanks suited for top-view appreciation, feeding, water temperature, and water quality management tips, plus how to source from breeders.
Key Takeaways
Explore the characteristics, history, and care methods of the Izumo Nankin, Shimane Prefecture's traditional goldfish designated as Japan's natural monument. Discover its distinctive compact body shape and beautiful four-lobed tail, how to select traditional vessels and tanks suited for top-view appreciation, feeding, water temperature, and water quality management tips, plus how to source from breeders.
The Izumo Nankin is a highly prized goldfish variety with a long history as a traditional goldfish of Shimane Prefecture and is designated as a natural monument of Japan. With its distinctive compact body shape and graceful swimming, it is also known among goldfish enthusiasts as a phantom goldfish. This article provides a detailed explanation of the Izumo Nankin's characteristics, history, care methods, and information on how to source them from breeders.
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What is the Izumo Nankin — Shimane's Phantom Goldfish
The Izumo Nankin is a Japanese native goldfish variety that originated in Shimane Prefecture (formerly Izumo Province) during the Edo period. Today, it is protected as a national monument (designated in 1982), and enthusiast groups centered in Shimane Prefecture continue to maintain and refine the breed.
Morphological Characteristics
The defining characteristics of the Izumo Nankin are its distinctive plump, short body shape and gracefully spreading four-lobed tail (some individuals have crucian-like tails).
Body Shape: Extremely short and rounded, with what is called an "egg-shaped" body form. Similar to the Ranchu but with a dorsal fin
Dorsal Fin: Present (the Ranchu lacks a dorsal fin)
Head Shape: The development of the head growth (wen) varies by strain, ranging from minimal to moderately developed
Tail Fin: The four-lobed tail is considered ideal, displaying beauty when opened horizontally
Body Color: Red, white, and red-and-white (calico) are the standard colors. Other colors are rarely valued in competition standards
Adult length is typically 10–15 cm. Smaller than the Ranchu, they are suitable for aquarium keeping.
Status as a Natural Monument
The Izumo Nankin is designated as an "Intangible Folk Cultural Asset of Shimane Prefecture" and a "National Natural Monument of Japan." While sale and keeping are not prohibited, there are restrictions on wild collection and commercial trading. Purchasing from enthusiast groups or authorized breeders is the appropriate sourcing method.
History of the Izumo Nankin
The origins of the Izumo Nankin trace back to the late Edo period. Goldfish brought from China during the period of national isolation were selectively bred and crossed repeatedly in the Izumo region of Shimane, resulting in the distinctive body shape seen today. The breed declined temporarily during the Meiji and Taisho eras, but preservation societies were established after the Showa period, protecting the breed to the present day.
Care Methods — Tanks, Water Temperature, and Water Quality Management
Selecting a Tank
The Izumo Nankin is bred with top-view appreciation in mind. While it is beautiful from side view as well, keeping in oval basins or traditional shallow Japanese vessels (Wabune) is common among enthusiasts.
Container
Characteristics
Wabune (30–60 cm)
Optimal for top-view appreciation. Standard choice for its aeration and ease of maintenance
Aquarium Tank (60–90 cm)
Side-view appreciation is also possible. Easier to install filters
Outdoor Plastic Basin
Suitable for outdoor summer keeping, but caution needed in winter
Water Temperature and Seasonal Management
The Izumo Nankin has relatively good cold tolerance and can be kept outdoors, but care must be taken as they are sensitive to sudden water temperature changes.
Ideal Temperature Range: 15–25°C
Summer: Temperatures exceeding 30°C are dangerous. Manage with shading, cooling fans, and water changes
Winter: Protection is necessary outdoors below 5°C. Indoor wintering is safest
Feeding
The Izumo Nankin has a short digestive tract with limited digestive capacity, making overfeeding potentially fatal.
Feeding Frequency: Twice daily (morning and evening)
Quantity: Only as much as they can consume in 5 minutes
Food: Goldfish-specific pellets or flakes (low protein, high fiber is ideal)
Live Food: Bloodworms are effective for color enhancement but should be limited to 1–2 times per week
Water Quality Management
The Izumo Nankin is sensitive to water quality changes. Perform water changes 1–2 times weekly, replacing approximately one-third of the total volume. Monitor ammonia and nitrite levels at least monthly to ensure stable water conditions.
How to Source from Breeders
The Izumo Nankin is rarely available at conventional pet shops. The main sourcing methods are these two:
Direct Purchase from Preservation Societies or Enthusiast Groups: Based in Shimane Prefecture, they sometimes offer sales at exhibitions and competitions
Purchase from Authorized Breeders via Online or Direct Sales: They may be listed on breeder-direct platforms (such as Brichoku). When shipping, proper packaging and temperature control are essential to minimize stress
When purchasing, check the body shape (roundness balance), tail fin spread, and body color (intensity of red and clarity of white). Raising from young fish (juvenile to 1 year old) makes it easier to become attached and allows you to enjoy watching their growth.
Summary
The Izumo Nankin is a prized breed representing Japan's goldfish culture. Its distinctive body shape and graceful swimming, unlike other goldfish varieties, leave an unforgettable impression once seen. While care difficulty is relatively high (especially regarding water temperature and feeding management), with careful handling they are a unique goldfish you can keep for many years. Engaging with preservation societies and breeders while keeping them opens the door to a deeper appreciation of goldfish culture.
