Teruyuki Hiroi

Marusaka Koi Farm is a long-established family breeder located in Ojiya, Niigata Prefecture, right in the center of Japan’s historic koi-breeding region. The farm has been active since the late 1940s and has grown into one of the larger and more diverse operations in Niigata. Even though Marusaka produces koi on a substantial scale, the farm has remained family-run for three generations, with each generation contributing to its reputation for quality and craftsmanship.

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The Breeder

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Today, Marusaka Koi Farm is managed by Teruyuki Hiroi, whose family has been breeding koi since the post-war years. Teruyuki carries forward the practices passed down to him, combining experience, observation, and careful selection. His approach is steady and traditional, but with an openness to breeding a wide range of varieties. He is known for maintaining consistent quality across the many types of koi produced at the farm.

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What They Breed

Marusaka is recognized for producing an unusually broad lineup of Nishikigoi. The farm is especially known for its metallic and Doitsu varieties, which are appreciated for their bright skin and strong contrast. Some of their signature varieties include Kin Kikokuryu, Kikokuryu, Kujaku, Lemon Hariwake, and other hikarimono. These fish often stand out because of their luminous skin quality and crisp patterns.

Beyond metallic koi, Marusaka also has strong traditional lines. The farm has long been involved in breeding Sanke and Doitsu Kohaku, which helped build its early name in the koi world. They also produce Midorigoi, Ginrin Chagoi, and other unique kawarigoi, making them a popular farm for hobbyists seeking something different.

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Farm Scale and Facilities

Marusaka operates on a fairly large scale for a family operation. They maintain around 80 mud ponds along with well-organized indoor facilities for fry, tosai, and parent fish. Each breeding season, they raise a large volume of koi, but they do so with careful selection and culling, allowing them to maintain solid quality across multiple varieties.

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Despite the size of the farm, the hands-on family approach ensures consistency from year to year. The Hiroi family takes pride in quality control and stays involved in all stages of breeding, raising, and selecting koi.

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Reputation

Marusaka is respected for being reliable, versatile, and consistent. Because they produce both classic varieties and striking metallic koi, they appeal to a very wide audience  from collectors looking for unique koi with eye-catching metallic skin to hobbyists who prefer traditional patterned koi such as Sanke or Doitsu Kohaku.

Their Kikokuryu and Kujaku in particular are often highlighted by dealers and koi keepers around the world. The farm’s broad selection, steady quality, and long family history make Marusaka a trusted and well-liked name in Niigata.

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Summary

Marusaka Koi Farm is a multi-generation breeder known for both diversity and dependable quality. Under Teruyuki Hiroi’s leadership, the farm continues to produce a wide range of koi including metallic, Doitsu, and traditional varieties. With decades of experience and a balanced approach to breeding, Marusaka remains a respected and popular farm in the koi community.