Koi are tropical freshwater fish that belong to the carp family. In fact, today’s beautiful and world-renowned koi were developed from common food carp by fish farmers in Japan over 200 years ago by selectively breeding the occasional fish found with some color or pattern on it. Today koi have become popular just about everywhere and are bred in every country. Currently, they are considered to be the most popular and most highly prized freshwater ornamental pond fish.
Koi and carp have always been very popular in Japan and China, and in most parts of Asia. Koi, and its direct ancestor the carp, have long been the stuff of legend in this part of the world. To the Japanese, carp and koi traditionally embody strength, courage and determination. The Chinese call koi the king of freshwater fish, and regard it as a symbol of good fortune and celebration. Koi are often referred to as “living jewels” or “swimming flowers” because of their tremendous color and color variations. All koi have similarly shaped bodies and fins, but they come in a variety of different colors and patterns such as gold, silver, orange, red, blue, black, white, and all kinds of combinations of these colors. All koi also come with adorable whiskers on their faces, called barbels.
Koi can grow up to 3 feet (36 inches) in length and can weigh over 5 pounds each! The growth rate and final size of your koi will also depend on water quality and conditions, feeding methods, and the size of the pond or how crowded the pool is. With optimum conditions, the average growth rate for a healthy koi is 2 to 4 inches at the end of the first year, 6 to 8 inches at the end of the second year, and 10 to 12 inches at the end of the third year. After the third year, the growth pattern slows down as the koi nears its maximum length.
Koi are very hardy and are fairly easy to keep, and also have a pretty long lifespan. Most koi can live at least 25 to 35 years, and with good water conditions and proper care, 50 to 100 years would not be unusual. In Japan, koi are frequently passed on to the next generation. The oldest known specimen, a red female named Hanako, was owned by Nagoya University President Komei Koshihara. Though Hanako died in 1977, a microscopic examination of one of her scales proved that she was born 226 years before her death in 1977 – she was born a few years before the United States made its debut as a nation!
To have the best quality koi that look the best and that are disease free, proper care is essential. Having adequate pond space is a very important part of this care. In fact, pond size is the main factor in determining how many koi you can keep and the quality of your koi. You can try to put half a dozen koi in 1000 gallons, but the koi will probably not grow very large or look very good. As a rule of thumb, every full size koi should have about 500 gallons to itself.
The other reason for having adequate pond space is that the smaller or more overcrowded a pond (or an aquarium) is, the lower the quality of the water. Overcrowding koi in a pond will contribute to fish stress, and greater potential for parasitic diseases and bacterial infections. Having adequate space in the pond will help the koi stay healthy and live long. The pond should also be deep enough, at least 3 feet deep. This will keep your pond cooler in the summer months, warmer in the winter months, and keep predators like raccoons and herons from eating your fish.
In the old days back in Japan, these gorgeous creatures were housed in lushly landscaped outdoor fish ponds. The ponds were constructed to provide adequate oxygenation and had a large turnover of water to ensure high water quality and filtration. With a little bit of energy and time, you can also create such an environment for your koi, or at least get pretty close to it. You can rely on either natural methods, mechanical methods, or a combination of both to achieve a healthy pond with proper aeration and filtration.
The natural method usually consists of planting some water plants in the pond to provide sufficient oxygenation and aeration for the fish, and adding a few scavengers such as snails and catfish into the pond for cleaning up wastes from the bottom of the pond. In addition to providing oxygenation and aeration, water plants also serve to further beautify your pond, help keep the water clear, and help reduce the growth of algae that can be unsightly and consume too many nutrients from the water.
If you find that your pond is not being kept clean and clear enough by natural methods, or if you plan to keep a lot of koi in the pond, you may want to use mechanical methods or a combination of natural and mechanical methods for the aeration and filtration of your pond. You would also probably need to use mechanical methods for aeration and filtration if you are keeping your koi in an aquarium, though aquarium use is not recommended for koi unless the aquarium is of a very good size. A good pump and filter system will filter the pond’s (or aquarium’s) entire volume every couple of hours, removing solid and chemical waste from your pond pretty much completely.
You can get filters that come with aerators built into them. These filters will return the water to the pond by a waterfall or fountain, which not only looks very nice but also aerates the pond extremely well. Another type of popular filter is the biological filter, which is a container that is usually filled with a medium on which bacteria will grow, and they would consume most of the waste from the water. Whichever filter you use, you should clean it at least twice a year to keep it working properly and efficiently.
With sufficient natural and/or mechanical aeration and filtration, cleaning or changing the pond water once a year in the early spring should be sufficient. However, if you notice your pond getting pretty dirty and overgrown with algae, or if you suspect chemical pollution, then you might want to change the water. In that case, change 20% of the water in your pond once a week or so for a few weeks. This simply means removing about 20% of the old water from your pond and replacing it with fresh tap water from the faucet. Avoid changing all the water at once. Scooping out leaves and other debris from the pond regularly using a net is another easy way to help keep the water clean and clear.
Overall, koi are remarkably hardy and healthy fish, much more so than even goldfish or other tropical fish. Koi can withstand a wide range of temperatures. Healthy koi can even survive under the ice in extreme cold as long as the water does not freeze solid. They will not move around or eat much if the pond water is very cold, basically hibernating. Needless to say, koi generally do not need heating. Of course, for optimum health and comfort of the fish, it is recommended that you avoid huge fluctuations in temperature and pH of the water, and perhaps use some heating during the winter months. As for food, feeding koi once or twice a day is good. There are a variety of pellet fish foods that are specially designed for koi. Koi can also be fed dried or fresh shrimp, lettuce, cooked rice or cooked oats.
Keeping koi requires some space and work, but raising them is a very fascinating and rewarding hobby. Their beauty, fame, hardiness, and longevity make them well worth it. For the avid koi enthusiast, there are koi shows in which koi compete according to their size and class, often for huge prizes. There are also hundreds of koi clubs throughout the U.S. and the rest of the world.