Being omnivores, koi have a diet that consists of both animal and vegetable food. With the many varieties
of koi food containing both of these matters, owners should be able to provide a healthy, balanced diet.
When purchasing food for koi, the food must be able to float for at least eight hours. Also, the water in a
pond must not turn cloudy for 48 hours, that is, if the fish are not eating. In order to provide food that is
safe and healthy for koi, owners should first test food in a glass filled with water. Owners should not let
faulty label claims stating that ”the water will not cloud” fool them. Every kind of fish food clouds, due to a
chemical reaction that takes place when food breaks down in the water.
The Food Role:
Like humans and other organisms, koi have metabolic functions that run on a nutritional basis. The food an
owner feeds their koi is used by the koi for two simple functions. First, the food is broken down into more
basic compounds. These simpler compounds are utilized as a foundation in the process of tissue growth.
Once enough compounds are used to fulfill the needs of replacing damaged tissue, the leftover compounds
are used as fuel. Finally, the material that is not used for fuel is stored in the body as fat, or exuded as
waste. The other simple function of koi food is the providing two basic energy forms. The first energy
form, basic energy, is needed at all times, so that the koi’s heart, kidneys, and other internal organs may
operate constantly. The second energy form, muscular energy, is used to drive koi through the water.
In the koi diet, the basic components are fat, proteins, and carbohydrates. Owners should however, add
vitamins and minerals to the koi diet. Proteins are compounds created by amino acid fusion. Some protein
is synthesized in the koi body. Others, however, are provided by the flesh of different animals. These
proteins are known as essential amino acids. Commercial food has been specially formulated to ensure
this. Protein rich live foods include: invertebrates such as earthworms, Daphnia-“water fleas”, aquatic
worms, and insects. Carbohydrates consist of simple sugars, or monosaccharides. They can be found in all
vegetable matter. Fats, made up of a crucial group of compounds, may be liquid or solid in their physical
state. They are in fact, the most efficient energy form. Older koi fish benefit from a fat increase, as they find
fats to be easy to digest. One of the downfalls of fats can be overconsumption, which may lead to fatty
liver disease. Vitamins, required in small amounts, are vital to fish. In the presence of heat, vitamins are
destroyed. Foods that contain the richest source of vitamins include: green plants, vegetables, liver, fruit,
and fish oils. Vitamin deficiency can result in: weight loss, poor bone structure, loss of fertility, loss of
appetite, stunted growth, inability to consume foods, and nervousness. While a deficiency is unfortunate, an
excess can be just as undesirable. In the body, not all vitamins are expelled. Therefore, some vitamins stay
within the body. This retention can cause an imbalance, which may prevent the usage of other vitamins.
Although koi need minerals in their diet, only a certain amount is required. However, the list of minerals
important to koi is extensive. Some minerals include: magnesium, copper, cobalt, zinc, sulfur, iron, iodine,
fluorine, molybdenum, and selenium. Calcium and phosphorous happen to be the most important though.
Calcium is needed in much larger amounts in comparison to the amounts of other minerals. It is extremely
important to the formation of bone structure. Typically, there is no need to present minerals in the diet
because they are naturally found in all foods and in water. One exception may be providing a calcium
supplement before breeding season. Like vitamins, minerals can be a deficiency or excess. Mineral rich
foods include vegetables like spinach, kale, and lettuce. Algal forms of plant life found in commercially
prepared foods contain many minerals.
Overall, a koi diet should contain 35% proteins of animal origin. The remainder of the diet should consist of
carbohydrates. Protein should be increased in amount in the diet of young fish. Commercial koi foods come
in many forms. Some include: flakes, cubes, granules, powders, and pellets. Live foods may be acquired
by: purchasing them from a local dealer, catching them in the wild, or by breeding them from cultures
supplied by pet stores. However, it is not required to supply live foods to koi. Providing koi with
commercial food will fulfill all of their nutritional needs.
Koi spend a considerable amount of time browse feeding and searching for food on the bottom of a pond.
They will eat any live food they may find. When koi are kept in ponds that do not have plants, it is crucial
to feed them often but in small portions. Koi should be fed at least twice a day, being once in the morning
and once in the late afternoon, or evening. It is a good idea to alternate the diet between higher protein
meals and meals with a large carbohydrate content. Avoiding feeding the same meal everyday will ensure
that koi remain interested in eating. When feeding fish, it is important to devote a few minutes to watch
them eat. Owners should observe the individual eating habits of all the koi in their pond. This way, if a
problem arises, they may trace it back to the eating habits of a certain fish. A shift in an eating habit is the
first sign of a problem with a koi fish. By observing fish eating for a few minutes, an owner may prevent
overfeeding koi. Doing so, an owner will be able to tell if their koi eat all of the food they give them within
five to ten minutes. If the koi do not eat all of the food in that time period, the leftover food then sinks and
decomposes, causing excess ammonia in the pond, which can be extremely harmful to fish.
The metabolism of a koi functions best at temperatures over 70 degrees Fahrenheit. Foods that are rich in
protein are hard for koi to digest when the temperature drops below 65 degrees Fahrenheit. Do not feed
koi when the temperature reaches over 90 degrees Fahrenheit.
Laguna Koi: http://www.lagunakoi.com/Koi-Feeding-Guide-Library-sc-334.html
Barrie, Anmarie. The Professional's Book of Koi. Neptune City: T.F.H. Publications, Inc., n.d.
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