The health, growth, and color intensity of are all dependent on water condition. A chemical examination should be made at frequent intervals and this analysis should include tests for: pH, water hardness, oxygen concentration and chemical content. Ten to twenty minutes should be spent every day checking the pond condition, especially in the morning.
This daily checking is very important for the health of your Koi.
Although many important things about Koi have been learned from well known Koi keepers in Japan, we cannot use 100% of their knowledge for our systems. For example, on the West Coast of the United States, mosily in the California area, the water has a high pH and is very hard, the opposite holds true in Japan. Also, water temperature in California is much higher.
Japanese Koi magazines often suggest the use of special kinds of minerals to combat problems. Trying to use those cures in one of our ponds could result in more problems. For example, Japanese Koi keepers use the high "Bakki" tower system (air and water turbulence system) to raise pH. If the same were used in parts of the U.S. pH would be increased to a point detrimental to the fish. They also suggest the use of oyster shells to neutralize the chemical content in the water. However, oyster shells would not be benefidal in hard water. The California area is much warmer and has much less rainfall than Japan therefore larger biological purification sytems are required.
Some Koi keepers in the United States use chemicals to control the water condition. This type of control requires the water condition be checked every morning and night every day because nature will change each second, minute, hour and day. The environment affecting the water changes continually. As a result the weather temperature, atmospheric pressure and chemical content in the air and the pH will change accordingly. A pH reading taken during the early part of morning might register low; however, after the mid afternoon, that reading will go up. In the same pond the water can show a change of as much as .5 to 1.0 on the scale.
The water condition can be stabilized if the pond and purification system is well designed. Do not bother with chemicals to adjust. Once it is stabilized by a good system, the Koi will adjust to the environment of the pond even though the pH maybe a little high and water a little hard. In effect, don't panic if the pH reading is high, more harm can be done to the Koi by adding chemicals to reduce it.
Some Nishikigoi such as those with black color patterns, ie.Showa-Sanshoku and Utsuri-Mono, do well in hard water as it is known for improving blacks. However, if the water is very hard, there is a possibility a Kohaku could get black spots on the body.
Most Koi keepers in the California area use the local urban water system. Although the oxygen content is high and presence of harmful bacteria very low, when added to the pond in large amounts, it maybe harmful to the color and health of the Koi due to chemicals added by the water company causing high pH and extreme hardness. The chemicals added include chlorine and chloramines. Although these chemicals kill bacteria, they also can kill the Koi. Therefore, large quantities of city water should never be added in a short time period. High water hardness is a critical issue because it can seriously affect the shine or gloss (Tsuya) of the Koi's skin and dull the color intensity. High pH and hard water can be overcome by use of a well designed purification system.
Large amounts of fresh well water are used by some Koi keepers to get by without a purification system. Even though well water is very cheap or free and without harmful chemicals such as chlorine and chloramine, a large amount of fresh water should not be put into the pond at one time. Carp like to live in the same water condition and environment. Japanese Koi keepers who have good quality Nishikigoi do not add large amounts of fresh well water to their ponds, even though it is readily available. If a quantity of fresh water is entering the pond, the Koi's body system has to adjust to the new water condition. A loss of shine and color fading can be a result of excessive water changes.
Water circulated for a long time without change becomes aged and can cause small bubbles and scum in the pond. Most purification systems cannot eliminate 100% of the harmful chemicals such as ammonia. It is suggested that 5% to 20% of the pond water should be exchanged every week and fresh water added. This fresh water should be added in small amounts on a continuous basis, 24 hours a day, to prevent a major environmental change in the pond. When the sediment tank and mechanical filter are backflushed, the water lost equals the amount of fresh water that should be replaced daily.
Clear water does not necessarily mean healthy water for Koi. Clear water is good for the eyes of the Koi keeper because the fish can be seen but harmful chemicals cannot. Carp are usually dwellers in muddy water and, consequenfly, Koi seem to enjoy the same conditions.