In the colder regions of the U.S. and Canada, when the temperature dips down into the freezing range, fish and plants can be left outdoors to hibernate naturally.
However, the freezing of the pond surface can create dangerous conditions for fish due to the accumulation of gas below the ice. Always ensure that there is a small hole in the ice cover, so that your fish, koi, or other inhabitants can breathe.
You should try to clean out as much organic debris as possible before the pond ices over and install an aerator, a de-icer, or a heater to keep a hole in the ice. Even the smallest of holes will suffice. This allows oxygen in for the fish and plants and also allows any toxins to escape. Whatever you do, do not crack the ice using a hammer or other device. This will shock the fish and cause undue stress.
Water Temperature vs. Air Temperature
Water takes a long time to heat or cool compared to the air. This is why it is important for pond owners to go by the water temperature and not air temperature when it comes to caring for your pond. Water temperature is the determinant for seasonal preparation as well as feeding schedules for your fish or koi.
At a water temperature of 60°F:
Thoroughly remove organic debris from everything.
Check power lines for cracks to prevent electrical hazards.
Inspect the seal of the outer pump housing for leaks.
Check the UVC bulb, which should be replaced annually.
At a water temperature of 50°F:
Stop feeding your fish.
Trim and move hardy lilies to deeper water.
At a water temperature of 40°F (before the first frost):
Move your frost-protected pump to a plant shelf to prevent lowering the deep-water temperatures and causing undue stress on your fish or koi
Store your non frost-protected pumps or anything, such as filters and uv clarifiers, that has glass or plastic inside, in a bucket of water in a frost-free location. This keeps the seals moist and debris residues from hardening.
Install an aerator, deicer, or heater.
Modern Technology Defies Freezing Weather
Winter is the biggest threat to a pond and its’ equipment. In the winter there is ice; ice expands and can burst pipes and filter housings.
Be sure to remove all points of the system where pressure can accumulate. Remove filter pads and lids from filters, allow for pressure relief in the system where possible.
The good news for pond enthusiasts: sub-zero temperatures cannot harm the AquaMax Eco Premium, ProfiMax, Neptun, or Profinaut pumps. They can be turned off but remain frozen in ice and snow without damage!
The following applies for all products that are not frost-proof: Safeguard them from winter conditions accordingly! You should take pond pumps and filters out of the pond before the first frost. Store them in a place that will not allow freezing.