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| Koi are domestic mutations of the common fresh water carp, Cyprinus carpio. These mutations first occurred in Persia and China around 500 BC. They were introduced into Japan by 200 AD where they became very popular. The selective breeding programs intensified by the Japanese, established today's color and scale patterns. Koi are large fish that can grow to a maximum size of 28 to 36 inches if maintained in proper systems. Since Koi need about 75 gallons of water per adult fish, they are best kept in ponds. If maintained properly, koi have long life spans often in excess of 50 years.
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Koi can withstand a wide range of water temperatures. However, they do better and exhibit more vivid colors when the water is maintained between 61 and 75 degrees. Water chemistry parameters for koi are similar to other freshwater fish. Koi prefer water pH between 7.0 and 8.5. Koi are very susceptible to chlorine toxicity. A chlorine level of 0.2 to 0.3 PPM of chlorine, which is found in drinking water, can kill koi within 20 days. Even very low levels (i.e. 0.002 PPM) can cause gill lesions. It is very important to insure that any water entering the pond is free of chlorine. Koi and carp have digestive systems adapted to a primarily herbivorous diet. Koi lack oral teeth but have paired teeth located back in the pharynx to grind swallowed plant material. Koi also lack a true stomach or pyloric ceca, which are found in most other fishes. The intestine length increases proportionally as the fish ages. Koi become sexually mature at about 12 inches in length. Koi, carp, and goldfish are vegetation spawners and can deposit hundreds of small adhesive eggs per spawn. Egg development depends on the ambient water temperature. Hatching can vary from 2 days at 86 degrees F to 7 days at 60 degrees. Allen C. Riggs, D.V.M., practices at Lower Keys Animal Clinic in Key West, Florida. He can be reached at 305 294 6335. | |
