Winter can be stressful on yourself as well as on your fish. Pre-planning and appropriate precautions can reduce the stress and assure success. Preparing you pond and koi for winter begins long before leaves begin to fall. The single most important consideration in assuring that your koi emerge satisfactorily from winter dormancy is their physical condition before cold water reduces their metabolism.
Because koi are cold blooded animals, their bodily functions (metabolism) are controlled by the temperature of the water. Metabolism is the chemical processes occurring within a living cell or organism that are necessary for the maintenance of life. Metabolism refers to all the physical and chemical processes in the body that convert or use energy, such as:
  • Breathing
  • Circulating blood
  • Controlling body temperature
  • Contracting muscles
  • Digesting food and nutrients
  • Eliminating waste through urine and feces
  • Functioning of the brain and nerves
During the latter days of summer you must assure that your koi build body mass from high quality food high in protein (Greater than 40%). Although your fish will eat almost any food you feed them, cheap foods do not satisfy the nutritional requirements and contain large amounts of non-digestible ingredients that cloud your water and makes your filter work harder. As the water temperature drops to below 60 degrees, food containing a lower percentage (less than 40%) of protein should replace the high protein diet. As the water temperature approaches 50 degrees you should decrease the amount and frequency of feeding a wheat germ based food. Once the water temperature reaches 50 degrees and stays below 50 degrees, all feeding should be discontinued. Even if daytime temperatures encourage fish activity do not be tempted to feed a small amount of food to the beggars. Don’t forget that your koi will not eat commercial food for several months and they must live off the body they have produced during the summer & fall. In order to know what foods to feed and when to begin and stop feeding you must have a reliable thermometer to measure the water temperature.
Another consideration is the quality of the pond water provided for your fish. A partial water change, ca. 20% before winter arrives is a good idea to improve water quality. Water changes of ca. 10% per week during the summer are also important to water quality and fish health. The addition of water to “top off” your pond is not the same as a water change. Water changes get rid of nitrates, phosphates and other chemicals that become concentrated as water evaporates. DO NOT forget to add water treatment chemicals such as Amquel or Novaqua to neutralize deadly chlorine and chloramines.
Leaves are a nuisance that must be removed before the pond is closed for the winter. All leaves and dead plant material must be eliminated before the pond is put to rest for the winter. The addition of water treatments such as MicrobeLift products will help clean the pond by digesting smaller particles of organic material that cannot be mechanically removed. The best course of action is to prevent leaves from entering the pond by installing a fine mesh net over the entire pond. A better solution would be to cover the pond with a plastic enclosure that resembles a green house. The structure will not only prevent the leaves from invading your pond but it will also keep the water warmer and moderate water temperature fluctuations. Although the net and “greenhouse” may detract from the appearance of the pond, they will provide a better winter environment for your fish.
Although the fish will be relatively in active as they line up in the deepest area of the pond they still require oxygen to survive. You must prevent the entire surface of the pond from completely freezing over to allow for toxic gas and oxygen exchange between the water and the atmosphere. Keeping a hole open in the ice can be accomplished by installing an energy efficient de-icer, an air stone or a pond heater. De-icers are thermostatically controlled to produce heat as the water temperature approaches freezing and will provide a hole in the ice the size of the heater. A pond heater will raise the water temperature to prevent freezing. Small ponds may be heated by installing one or several submersible aquarium heaters. Larger ponds will require the use of a heat ex-changer to raise the water temperature. The third option is to install an air pump and one or several air stones depending on pond size. The air bubbles will create agitation at the waters surface that will prevent freezing in all but the most extreme temperatures.If possible, aeration devices should be moved from the bottom of the pond to near the surface. If you have a waterfall, the falling water will keep ice from forming at the point of entry; there are two disadvantages of running your waterfall during the winter. The first concern is that you will be cooling the water as it flows over the rocks in contact with the cold ambient air. The second is the possibility of ice forming on the waterfall and diverting water off the waterfall and possibly emptying the pond. If you will maintain water circulation during the winter it is best to bypass the waterfall and introduce the returning water directly into the pond.
The use of filtration during the winter has been the subject of many lively debates. The primary concern is water freezing in the plumbing. You may think that as long as the water is moving it will not freeze. That may be true in your pond where you have a large volume of water, but there is a totally different situation in water flowing through un-insulated pipes. In extremely cold weather, the sub-freezing air will constrict the diameter of your plumbing pipes much the same way cholesterol obstructs your blood vessels. The pipes will eventually become completely frozen and your entire system will be in jeopardy of freezing and breaking pipes, filters, UV’s and pumps.
If you can monitor your system daily, it would be best to keep your filter system running all winter. The bacteria in an active filter system during the winter will continue to digest waste (fish continue to produce waste during the winter) and facilitate spring start up. Not all the bacteria die during cold weather and the live bacteria in the filter accelerate spring start up. It takes years for a filter system to fully mature and if you shut down the system for the winter, you start the cycle all over again each spring. To reduce the possibility of breakage, UV sterilizers should be removed from the system and a bypass pipe installed in place of the UV body.
Should you elect to shut down your system for the winter you must assure that all pipes and equipment are drained dry. If necessary, pipes that do not drain completely by gravity should be blown out with air. The filter should be cleaned before the shutdown and drained of water.
Each system is unique and appropriate procedures must be developed to assure a safe shut down. If you are unable or unwilling to perform the necessary winterization of your pond you may call us for assistance. We understand different plumbing and filtration systems and can put your mind at ease by properly your pond for the cold weather ahead.
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If you would like us to winterize your pond please call to get on the schedule for November.
Your fish will go dormant for the winter, give them the best environment possible to ensure a healthy start up in the spring.
Check back for more Koi keeping tips.
Please call if you have any questions. 

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Koi Pond Winter Keeping Tips

Winter can be stressful on yourself as well as on your fish. Pre-planning and appropriate precautions can reduce the stress and assure success. Preparing you pond and koi for winter...

Total Alkalinity Tester (Taylor Brand)


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