Top 10 Mistakes When Winterizing Your Pond

It’s that time of year again. Should you leave your pond fish outside? Or should you find a winter home inside for them? Whatever you choose, avoid unnecessary fish death, stress, or equipment failure with these points.

Here is a quick snapshot of the top 10 mistakes pond owners make when winterizing their ponds.

1. Winterizing Too Late

Many people wait until first frost to winterize their pond. In some cases, this can be too late.

As soon as temperatures drop below 10 degrees Celsius consistently, day and night, you’ll want winterize. Especially in the cooler Canadian climates, which can be unpredictable, it’s best to winterize your pond as early as September. You may get away with later (or less) winterizing in Southern Ontario and parts of BC.

You don’t want your pond freezing solid before you have time to prepare it. 

2. Letting Your Main Pump Run All Winter

Since water expands when it freezes into ice, even a little bit of water inside your pump, hose, or skimmer can ruin the equipment.

Drain your pond pump, hosing, and skimmer of as much water as you can before the weather turns to freezing. In turn, bring your pump inside or in a partially heated garage, to ensure no weather damage occurs.

If you have fish you are keeping in the pond all winter, you may need to run a pump all winter. AquaForce Pond Pumps allow you to adjust the nozzle which may be pointed up to help maintain an open hole in the ice. This may not be enough to keep a hole open in extreme winter conditions. 

AquaForce Pump and hole in ice

If you are looking for a more cost effective option, choose a smaller pump just to circulate water for your fish. Running all winter, a smaller pump will save you money on power costs.  

NOTE: If you are not winterizing your pond fish, skip ahead to #9

3. Feeding Wrong Kind of Food

As the temperature cools, fish require less energy. Since fish are cold-blooded, they also have different digestion needs. When the temperature drops below 10 degrees Celsius at night, feed your fish spring & fall food. These are easier to digest for your fish, and will prepare them for hibernation.

As your fish go into their hibernation-like state over winter, their metabolism decreases dramatically. When the temperature is consistently below 10 degrees Celsius, fish no longer need to be fed.

4. Leaving Fish Out in a Too Shallow Pond

While the proper equipment can remedy a too shallow pond, there is no protection for your fish or equipment in the case of a power failure. As a good preventative measure, make sure your pond is at least 2 or 2 and a half feet deep before leaving your fish outside. This way, your pond will not freeze solid very quickly in the case of a power or equipment failure.

5. Letting the Pond Freeze Over

Even with a pump running, extreme temperatures can freeze your pond over. This can mean gas exchange will stop, and toxins from fish respiration and decomposition can kill your fish.

Install a thermostatically regulated pond heater, such as Aquascape Pond De-Icer, to keep a small area open at all times.

Monitor your pond for ice coverage regularly, whether you are running a pump, aerator, or heater.

6. Letting Too Much Debris Fall in Pond

Leaves and debris in pond

Keep your pond clear of debris: including loose grass, leaves, sticks, and other organic material. While it accumulates throughout the year, pay special attention to debris in the fall. Surface pond skimmers, skimmer nets, and pond vacuums are all handy aids. Protective pond nets are also very helpful, especially in fall when the leaves are falling.

If you allow too much debris to accumulate in your pond, it can decompose in your water. This releases toxins in your water, even in the winter. These toxins can stress or even kill your fish, and cause algal blooms in the spring.

7. Using the Wrong Pond Heater

When choosing a pond heater for over the winter, it’s tempting to use standard commercial pond heaters. These are typically a high wattage heater sold at a tempting low price. However, resist the urge to use these stock heaters on your pond!

These high-wattage heaters can heat your pond too much, and in a period of consistent warmer weather, can create an artificial spring. This can get your pond fish out of hibernation, offsetting their natural balance.

Laguna Pond Heater

Pond heaters designed for your pond are typically of a much lower wattage (300-500W compared to 1500W). They are controlled by thermostat, so they will only heat when necessary. While more expensive initially, low operating costs will save you money over the winter.

8. Putting Pump on the Bottom of Pond

Pumps are useful for water circulation and gas exchange, but proper placement is crucial. When winterizing your pond with fish, place your pump at least one foot off the bottom of the pond. You want the bottom of the pond to be completely still. Your fish will lay under the pump in the stagnant water, almos like they are hibernating.

Center placement of the pump is important, so use a block and secure your pump to it.

NOTE: The following steps are for bringing your fish inside

9. Feeding Fish Too Much

When you bring your fish inside for the winter, make the transition slow. Leave the fish in a bucket of pond water with an air stone for a few hours. Then, place them in a bag in the aquarium or tub that will be their winter home.

Do not feed your fish for at least 2 weeks after bringing them in the house! Your fish are in hibernation mode (or close to it), so it takes a bit of time to get their systems used to the new climate. Otherwise, you can shock their systems!

An ideal winter home for your fish would be in a garage or cold storage kept between 5 and 10 degrees Celsius. You would not need to feed them at this temperature.

10. Testing Water Too Sparingly

Testing water is always good practice with a pond or aquarium. Pay special attention to ammonia levels when you are transferring your fish from your pond to an indoor home. Fish metabolism increases in warmer temperatures, and your fish are most likely moving to a smaller winter home. Laguna Quick Pond Test Strips are convenient and easy-to-use.

Make sure there is enough space in your fish’ winter retreat. Fish can grow twice their size in the summer, so plan for the extra inches. An inch of fish per gallon is still your best bet.

Set up your over-winter tank or tub at least a month in advance, and keep a few fish in there to set up the nitrogen cycle.

Lastly, add plenty of Nutrafin Cycle to offset the ammonia.


Avoid these common pond winterizing mistakes to avoid stressing your fish, breaking your equipment, or worse. Happy winter!


Related Winterizing Articles: 


Relate Pond Winter Supplies:

  • Protective Pond Netting - Help limit the amount of debris that falls into your pond.
  • Heaters & De-Icers - Helps keep a hole open in the ice for gas exchange.
  • Aerators - Paired with a heater or deicer, aerators provide gas exchange and keep a hole open at the surface.
  • Small Pumps - Saves on energy consumption, and provides appropriate circulation.