Karashigoi are legendary for their growth and appetite. Learn about this mustard-colored koi variety and its friendly temperament.
The Karashigoi is a relatively modern addition to the koi world that has quickly achieved legendary status among collectors who value size and vigor. Developed by crossing a Kigoi (a non-metallic yellow koi) with a Chagoi, the Karashigoi inherits the best traits of both parents. Its name is derived from "karashi," the Japanese word for mustard, reflecting its distinct yellow-to-orange coloration. Like its Chagoi ancestors, the Karashigoi is an eating machine, possessing a metabolism that allows it to grow at an astonishing rate. It is not unusual for a Karashigoi to put on several inches and significant weight in a single season, often outpacing every other fish in the pond. This rapid growth is matched by a bold and curious personality. Karashigoi are exceptionally friendly and will often wait at the edge of the pond for their owners, begging for food with a level of enthusiasm that is truly charming. Their intelligence is high, and they are frequently used by breeders and hobbyists to "train" other fish to be less fearful of humans. Visually, the Karashigoi offers a warm, sunny splash of color that contrasts beautifully with the blue or green water of a typical pond. While they are solid-colored, their scales often exhibit a clean, reticulated pattern that adds depth to their appearance. Breeders such as Konishi have become world-renowned for their Karashigoi, producing koi that are not only massive but also possess refined body shapes and consistent skin quality. Because they are so hardy and grow so quickly, they are often recommended for those starting a new pond who want to see immediate results. However, their large size means they require significant filtration and plenty of space to swim. Owning a Karashigoi is a commitment to providing a high-volume diet and a spacious environment, but the reward is a magnificent, golden-hued companion that will likely become the friendly centerpiece of your aquatic collection for many years to come.
Keeping Karashigoi koi in Southern California
Chagoi grow quickly and can pass 36 inches, and big fish are often the first affected when oxygen runs low. Strong, round-the-clock aeration matters most for large koi in a SoCal summer.
Summer is the main growing season, but every meal adds waste and uses oxygen. In very warm water, feed less rather than more.
Summer care for every koi in SoCal
- Warm water holds less oxygen, yet koi need more oxygen as the water warms. That makes summer the season when oxygen runs shortest.
- Oxygen is usually lowest around dawn, because plants and algae use it up overnight. In summer, keep air stones, waterfalls or fountains running day and night.
- When oxygen runs short, large fish are often the first affected. The bigger and faster-growing your koi, the more aeration matters.
- Published "ideal" ranges vary between sources, from about 59–77°F to 68–78°F. Most sources treat the low-to-mid 80s °F as the point where you should cut feeding, add shade and add aeration.
- At about 82°F and above, feed less than usual. Koi can lose their appetite at 86°F and above, so offer small amounts of an easily digested food and remove anything left uneaten.
- Shade part of the pond, but not all of it, from the afternoon sun. A shade sail, pergola or floating plants will do. Don't enclose the surface so tightly that air can't move over it.
- Inland SoCal is much hotter than the coast. NOAA's 1991–2020 normals give an average July–August afternoon high of about 95–97°F in Riverside, 83–85°F in Santa Ana and 75–77°F at LAX (air temperature). Inland ponds therefore need the heat measures above sooner and for longer.
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