Preparing Your Koi Pond for Winter
Koi fish are cold blooded or Poikilothermic. The metabolism of koi depends on the temperature of the water that they are living in. In the summertime, koi are ravenous eaters and are also very active, but in the winter when the water temperatures drop, koi go through a type of hibernation period called torpor when they move very slowly, have a much lower metabolism and require less food. In winter, koi spend most of the time just treading water at the bottom of the pond where the water is warmer, although they move some to keep their joints from seizing up.
You can improve the winter eco-system for your koi when winter is approaching and even if it gets icy in your area.
What Do Koi Do in the Winter?
As autumn approaches, koi will start eating less food and their amount needs adjusting. When your pond water reaches about 50 degrees F, the metabolism and digestive systems of your fish will enter torpor. Koi may come to the surface of the pond where there is an ice opening in winter instead of just treading water in the deepest and warmest part. This allows them to get extra oxygen when the temperatures are freezing.
Is a Frozen Pond Dangerous to Koi?
Surface ice in a koi pond actually helps to serve as a layer of insulation to the deeper waters in the pond. However, a totally frozen pond doesn’t allow gas exchange on the water surface–meaning that oxygen can’t enter the pond and harmful gases, such as carbon dioxide can’t leave the pond water. A slow buildup of carbon dioxide and lack of oxygen can harm your koi.
Beneficial bacteria are hard at work over the winter and they require oxygen to break down the organic waste. Without enough oxygen, you will have a large amount of harmful waste in the spring. Slow digesting bacteria build up a large amount of products such as carbon dioxide and hydrogen sulfide. The combination of these two chemicals together can make your koi sick and have a smell of rotten eggs in the spring.
Winter Feeding Guidelines
During winter, your koi will survive on the fat they’ve stored from summer feeding frenzies. You can slowly start decreasing the amount of food they eat in autumn when the temperatures start to drop. A rule of thumb is to cut back to feedings only 2 to 3 times a week and when water temperatures reach 55 degrees F and remains there for more than a week, you can stop feedings all together.
Should I Turn off My Pond Equipment in Winter?
You can run your pond filter and pump in the winter if the temperatures don’t drop low enough for the water to freeze inside the pipes and equipment chambers. In very cold areas, water will freeze in the pipes and expand to cause damages and cracks to the pipes, filter boxes and pumps. Therefore, this depends on how cold it gets in your area.
Waterfalls and fountains can provide extra aeration and may keep your koi pond free of ice, but they are also heat exchangers that cool the pond water greatly. Waterfalls and fountains are a major cause of heat loss at the water’s surface and they stir up the warmest water and the deepest part of your pond. Therefore, it’s recommended to turn these water features off in the winter.
Install a Pond De-Icer or Heater
It’s beneficial to the health of your koi to install a de-icer before the pond freezes over. It keeps an air hole open so that gas exchange can take place and keeps ammonia build up from occurring in the pond to create serious stress to your fish. Install the heater before the surface of the pond is entirely frozen. The heater floats on the surface and slightly warms the water around it to keep an air hole open all winter. If you notice, you may even see your koi hugging up next to the heater to get additional warmth in winter.
Add an Air Pump
Adding an air pump to your pond before it freezes over will make many improvements along with a heater. It provides extra oxygen, movement and aeration to help prevent ice from forming. Installing both an air pump and a heater will create a more comfortable environment for koi throughout the winter.
Add Koi Friendly Bacteria
In the fall, when temperatures are starting to drop, it is important to add beneficial bacteria to your pond water to help with waste over the winter. This type of bacteria when added to your water helps to control harmful buildups of ammonia, sludge and fish waste of all types. It’s best to have a very clean pond before going into the cold temperatures of winter so that your spring cleanup time, when you reopen your pond is much easier.
Praziquantel for Fish Health
The most common koi fish parasites are flukes. Most people new to having a koi pond don’t realize that their fish are at a higher risk of bacterial and parasitical infections during the winter. When koi go through torpor and their digestive system slows drastically when compared to the summer months, their immune system is much more vulnerable. If there is an infection before winter and it is not treated proactively, you will have very sick fish in the spring. This is why it’s best to treat your pond about 2 months before the temperatures drop to 50 degrees F with praziauantel. This timing allows your fish to fight off any current bacteria or parasites they may have already before the temperatures drop in the winter. It also provides better immunity over the winter because the treatments usually have a long period of immunity afterwards. It is also important to use praziquantel in the springtime after opening your koi pond for the maximum immunity and best health of your fish.
Following these guidelines can help you to maintain the health of your koi pond all winter long, even in freezing temperatures so that they have a healthy environment all year round.