Marusei

Marusei Koi Farm –

Founded in 1960 by the late Seitaro Hirasawa and now managed by his son Yoshiyuki Hirasawa, Marusei Koi Farm is one of the largest and most influential koi farms in Japan. Situated in Kawaguchi, Nagaoka, Niigata Prefecture, the farm spans an impressive 100,000 m² and operates more than 200 mud ponds, supported by a parent stock of around 200 koi. With an annual production of approximately 200,000 fry, Marusei has earned its reputation as a koi farm that combines sheer scale with high-quality results.

What truly sets Marusei apart is its unmatched diversity of varieties. Unlike many farms that specialise in just one or two lines, Marusei has developed expertise across a broad spectrum, offering koi for every collector’s taste. Their production includes the classic Go-Sanke (Kohaku, Sanke, Showa) alongside a dazzling array of other varieties such as Kujaku, Kin Matsuba, Karashigoi, Hi Utsuri, Chagoi, Benigoi, Mizuho Ogon, Asagi, Aka Matsuba, Shusui, Yamabuki, and Kawarimono. This makes Marusei one of the most versatile breeders in Niigata, producing koi that appeal to both beginner enthusiasts and seasoned collectors alike.

Marusei koi are admired worldwide for their robust body shapes, excellent growth potential, and outstanding skin quality—traits that reflect decades of selective breeding and careful husbandry. Their Karashigoi and Chagoi in particular are highly sought after for their size and docile temperament, while their metallics and patterned varieties continue to impress with vibrancy and clarity.

Beyond their scale and variety, what defines Marusei Koi Farm is a commitment to refinement. Each year, tens of thousands of fry are carefully culled to ensure that only the very best koi are raised on, a process that balances their high-volume production with a dedication to excellence.