As winter sets in and the ponds freeze over with snow, many wonder: do the fish survive? The reassuring answer is yes — but only under certain conditions.
Surface ice forms because water reaches its maximum density at 4 °C. The colder water stays above and freezes, while the deeper water remains liquid. Beneath the ice, temperatures stay fairly constant, typically between 2 and 4 °C. This stability allows fish to slow down their metabolism and enter a period of winter dormancy, often referred to as a sleep of the aquatic world.
The fish become nearly immobile, use very little oxygen, and hardly feed at all. Native species — such as carp, roach, pike, and bream — are well adapted to these conditions. Snow and ice do not directly impact the fish, as they live beneath the ice layer in liquid water.
The greatest danger during winter isn’t the cold, but rather through-ice suffocation. A thick layer of ice and snow blocks out sunlight, preventing aquatic plants from photosynthesizing. At the same time, the breakdown of organic matter consumes oxygen. Under these conditions—particularly in small, shallow ponds (less than 60–80 cm deep) or those filled with silt, fallen leaves, and algae—winter kills can occur.
By following these simple tips, you can ensure your fish survive the winter safely in a frozen pond.
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