Frequently asked questions

What Differentiates a Koi From a Regular Goldfish?

While both Koi (cyprinus carpio) and goldfish (carassius auratus) come from the same family of fish, there are distinct differences in their appearance and breeding. Koi can grow from one or three feet in length, depending on how and where they are bred, whereas the goldfish will remain relatively small. While breeders of Koi have focused more on their color lineages, goldfish breeders have focused more on their body type.

Koi offer an almost limitless array of colors and designs compared to the relative simplicity of the few colors offered by goldfish. While the body contours of the Koi are uniform with an elongated body and whisker-like barbels, goldfish usually have wider and rounder body styles, with a variety of fin and tail types. Koi have a connected dorsal fin and tail, whereas the goldfish has two sets of paired fins and three sets of single fins. Goldfish can also have single or double tails.

How Do Domestic and Japanese Koi Differ?

Domestic Koi are bred in the United States, whereas Japanese Koi are only bred in Japan.

Japan is where Koi keeping and standards originated. Many Japanese Koi breeders have been breeding Koi for several generations and have cultivated larger fish with colors and bloodlines that exist nowhere else in the world. The best Koi are judged by their color, luster, and lack of physical defects. Consequently, Japanese Koi are considered superior to domestic Koi.

What Do Koi Eat?

In the natural wild, Koi would eat a variety of algae, worms, insects, seeds, plants, or anything they would find on the bottom of their habitat. If your pond is an ecosystem pond, they will be able to continue to eat a natural diet. But if not, pond Koi must be fed quality food that they are not able to get in the wild to maintain their health, longevity, and beauty.

Some common food that people feed Koi includes spirulina algae, wheat germ, brine shrimp, shrimp, worms, larvae, tadpoles, and commercial fish food. There are many quality foods on the market specifically designed for maintaining healthy Koi, coming in different sizes as well as pellets designed to sink or float. Koi should never be fed more than they can eat in a 10-minute session. They also should not be fed once the water temperature falls below 55 degrees Fahrenheit.

How Long Do Koi Live?

Although you may have heard that Koi can live for over 100 years, the reality is different depending on their habitat, the skill of their keeper, and what predators they may encounter.

Koi that live in the most optimum conditions with appropriate pH levels, nutrients, and low-stress environments can live well into their 50s, 60s, or even their 90s. The oldest Koi on record, Hanako, reportedly lived 226 years and died in 1977. But those fish that are kept by novice keepers often succumb to disease and have reduced life spans due to the keeper’s lack of knowledge. Koi kept by knowledgeable keepers are more likely to live several decades and often outlive their humans. The more time, knowledge, care, and maintenance a keeper is willing to devote, the longer their fish will live and healthier they will be.

What Pond Habitat is Best For Your Koi?

The ideal habitat for your Koi will be a large pond of at least 1,000 gallons containing natural elements such as smooth gravel, rocks, and hearty aquatic plants. It should be at least three to four feet deep in areas so your Koi can find cooler water in hot summer months. Koi require good-quality, oxygenated, well-filtered water that should be tested regularly for ammonia and nitrite, especially during the summer months.

When designing a Koi pond, you will want to consider the long-term size of the fish you want to keep to ensure that they have enough room to be healthy and happy. The pond should be stocked depending on the Koi’s expected full-grown size, not the size they are currently at. Koi will grow to the size that they are genetically designed to grow, not to the size of the pond.

Can Koi Survive Through the Winter?

Koi are considered moderately cold-blooded fish and thrive best in water temperatures between 59 and 77 degrees Fahrenheit. The Koi’s metabolism will match the temperature of the water they are in and in the cooler months, they will spend most of their time at the bottom of the pond where the warmest water is.

There are limits to how long a Koi can survive in its outdoor pond without some added assistance. To keep Koi in their outdoor pond through the winter, the pond must have adequate access to oxygen and should be equipped with a de-icer and air stone or a heater. Some Koi keepers set up tanks in their home or garage and move the Koi indoors for the winter. But it is essential to have a large enough setup for the fish when they are moved indoors, or they can quickly outgrow their space.

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