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Keep Your Fish Happy During the Winter

Pond pump pieces on on top of rock by pond

To ensure your Koi and other pond fish friends enjoy their winter slumber, a couple of things should be done prior to when the cold weather really sets in.

  1. Properly feed your fish

  2. Remove plant material from your water feature

  3. Add a pond de-icer

  4. Add aeration

It’s also important to monitor your water feature throughout the winter to make sure your fish are doing well!

Feeding your fish

Use a pond thermometer to help adjust fish feeding and water treatment applications.

As the cold weather comes, a fish’s metabolism starts to change. Since Koi and goldfish are cold-blooded, their digestive tract fluctuates depending upon their surroundings. This means that your fish will start eating less as the temperature of your pond water starts to decrease. Feed appropriately, taking note of the pond water’s temperature.

Pond thermometer

Keep track of the temperature of your water using a pond thermometer. A pond thermometer becomes particularly handy during the spring and the fall. It can help you determine when to start or stop feeding your fish and what to feed your fish.

At 15°C (60°F), you can switch from a protein-based food to more of a wheat germ-based food. At this temperature, the fish’s metabolism and digestion begins to slow down. Wheat germ-based food is easily digested and hence easier on your fish’s slowing digestive tract. We recommend Aquascape’s Cold Water Fish Food once the water reaches this temperature. One thing to definitely remember is that once the water is consistently under 10°C (50°F), stop feeding your fish. Their metabolisms will be very slow at this point as they are almost ready for the winter. The fish will be good all winter, surviving on their stored nutrients, and should not be fed until the pond water consistently reaches a temperature of 10°C again in the spring.

As always, all the food that you put into a pond should be consumed by the fish within 5 minutes. Whatever is not eaten after 5 minutes should be scooped out.

Remove plant material from your water feature

Stop leaves from decomposing in your pond by using a net.

In the fall, try to remove as much as possible any leaves and dead plant material from your pond. Decaying plant material can cause poor water quality which is not good for your fish. Trim back your marginal aquatic plants and lilies and make sure to scoop out any leaves that do not go into your skimmer.

The easiest way to prevent leaves from decomposing in your pond is to invest in a pond net that drapes over the pond and stops the leaves from getting in. Make sure to install the net before the leaves fall and make sure to blow off the leaves from the net throughout the fall. If you don’t blow off the leaves, the weight of them can cause the net to sag. Once the net sags, the leaves end up sitting in the water where they can begin decomposing. After all the leaves have fallen, remove the net.

Ensure proper gas exchange with a pond de-icer

A pond de-icer allows for toxic gas to escape.

Add a pond de-icer to your pond to ensure your fish’s safety through proper gas exchange and oxygenation. Despite popular belief, a de-icer is not used to keep the water warm for the fish. Instead it is used to keep a small hole in the ice so that harmful gases can escape. If ice fully covers a pond, then toxic gases can’t escape.

Pond deicer surrounded by snow

One concern we hear from pond owners is that they are worried about their electricity bill. With rising rates, we completely understand this concern. At the store, we sell the Aquascape 300-Watt Pond De-Icer. The benefits of this particular de-icer is its low wattage and its ability to turn on and off when necessary. The de-icer goes into off mode once it reaches a temperature of 21°C, reducing its energy consumption. The LED light on top of the de-icer will let you know when it is heating and when it is in off mode.

To further decrease your energy consumption, you can always choose to unplug the de-icer and only run it when you notice ice closing in over top of the pond. The water directly above the aerator will usually be the last to freeze over. Just watch this spot and when the ice is closing in, plug your de-icer in to keep the ice at bay. Keep in mind, this route will require you to pay close attention to your pond during the winter.

Add aeration to your pond

Although the de-icer helps oxygen to reach the surface of the pond, an aerator is required to make sure that oxygen is placed directly into the water. When your feature is running, the waterfall brings into the pond the oxygen required for your fish to breathe. Now that the waterfall is shut off, we need to replenish that lost oxygen.

I’m sure you’ve seen an aerator working before in an aquarium. Picture that neat bubble curtain or that oyster/treasure chest that would suddenly open letting a bunch of bubbles out.

Water tank with toys and fish

Just like that tiny treasure chest, an aerator for your pond has a motor which pumps oxygen through to a diffuser which sits in your pond. The diffuser breaks up the steady flow of air to create little bubbles which provides oxygen to your fish.

Pond pump pieces on on top of rock by pond

At our store, we carry the Aquascape Pro Air Pond Aeration Kits. We find these kits don’t have a lot of the issues that other aerators do. The tubing is freeze-resistant and doesn’t pinch, while the diffusers are heavily weighted and durable. The compressor has a heavy-duty metal housing to it however we do recommend putting some sort of covering over it in case you may need to access it.

Throughout the winter

During the winter, we sometimes have periods where there is no electricity. Usually Koi and other fish are able to withstand a bit of time without the aerator or de-icer working. However, if the electricity is out for a long period of time, be sure to have a backup electricity source. If the water does fully freeze over, do not break a hole into the ice. Remember when you were told to not tap the glass of an aquarium? Well, the same rules apply here. By breaking the ice, you can send shock waves through the water that can seriously harm your koi and other fish. Instead, create a hole by pouring boiling water onto the ice.

These recommendations are for pond owners who have decided to turn off their pond for the winter and live in a cooler climate. If you live somewhere warmer or have chosen to leave your pond running during the winter months, then different precautions need to be taken.

If you have any other questions, please feel free to visit our store as we would be happy to help!

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