Koi are a variety of the common carp that were developed by the Japanese over 2000 years ago. They were originally bred only for food; protein supplements for the largely vegetarian Japanese diet. Today, they have gained the reputation of being some of the most beautiful fish in the world, and they inhabit fish ponds built especially for them to compliment garden settings everywhere. They are called the national fish of Japan and are often described as works of art referred to as “living jewels” or “swimming flowers”. Koi lovers have created many organizations across the globe, and annual Koi competitions are held to determine who has the most beautiful of these fascinating fish. 

Most collectors value size in Koi. They can range in size from four inches to three feet long, but it will vary based on a number of conditions including the size of pond the Koi live in and the quality of food, water and environment. Koi can grow rapidly under the right conditions, and it is not uncommon for a fish to grow up to six inches or more a year. Koi come in a multitude of varieties. They are classified based on their many bright colors and patterns that they can develop. 

Koi are more than just mere eye candy however. They can make excellent pets as well. The fish are smart, and have the ability to show a range of emotions. They can even be trained to eat right out of their owner’s hand. As well, Koi have excellent hearing that is three times better than standard fish, and they have an abundance of taste buds all over their bodies, including their lips, tails and fins. Koi can show they are under stress by “blushing”, in which a bright red appears in the fins and on their bodies. Blushing can occur when handling a frightened Koi, or if the fish’s pond environment is poorly maintained. 

Koi are voracious eaters, and will overeat at every chance they’re given. They have been known to flop up on lily pads to retrieve bits of food as well as skim, dolphin-like, across the surface of the water grabbing for food as it is thrown to them. This is a comical, yet dangerous quirk of the Koi. The danger lies in the amount of ammonia the fish produces when it eats in abundance. Ammonia is produced and released into the water as the fish eats through gill respiration and in the fish’s urine and feces. If an owner is not careful with how much food they feed their Koi, the ammonia levels in a Koi pond can quickly escalate, turning it into a toxic soup and endangering the fish. 

If Koi are fed carefully, and their pond is cleaned and maintained regularly, they can be an excellent addition to any garden or landscaping effort. They are colorful and beautiful, and each one offers a unique personality that will often surprise those unfamiliar with the fish. Koi not only add to the beauty of any garden, but they make great pets as well.