There are various trains of thought as to whether a pond pump should be switched off and removed during the winter months. However, we at Water Garden Ltd have always firmly advised to keep the pump running for a number of reasons.
Firstly, a fish pond should not be left to stagnate. Secondly, we advise running water through the filter to continue to extract debris and, until the water drops below 6-8ºC, we’d also advise keeping the UV clarifier running to kill off pathogens even if single-celled algae is no longer breeding. In a fish or Koi pond, it is a good idea during winter to elevate the pump around 30cm (1ft) from the base of the pond so that the lower section remains tranquil and slightly warmer than the surface water which will be of benefit for the fish entering into semi-hibernation. Finally, any water which ripples the surface or cascades into the water is less likely to freeze, keeping a pocket of water ice-free to allow toxic gasses to exchange at the surface.
Many of the OASE Pond Pumps we supply are capable of operating at temperatures as low as -20°C which is well below the expected temperatures facing ponds in the UK. The only time we would recommend switching off and removing the pump is where the water is so shallow that if this freezes over it could potentially crush or damage the pump if expanding ice were to force upon it. However, this tends to be in very shallow ornamental water features rather than fish ponds so these can easily be drained as there are no fish or wildlife inside.
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