Pond fish are having a hard time in cold winters. Filters will function with difficulty owing to ice formation, as a result of which there is less oxygen in the water, whereas it will become more filthy. The solution id to provide warmer pond water. Using a pond heater you can heat the water in a pond and clear it of ice locally or keep it clear of ice during the period of frost. Owing to the ice-free opening the pond water will absorb oxygen and harmful gases will be removed.
Koi can not without a pond heater
With pond heating your fish will better get through the winter, they will have more resistance and the chance they will be affected by bacterial infections is poorer. Koi lovers who love to see their fish grow up as soon as possible can not do without heating, for below 8° C growth of fish will stop, while using their fat reserves. Watch the temperature of the water using a pond thermometer.
With a pond heater you can use the filter equipment also during the winter season. The warm water will stimulate the development of micro-organisms and consequently the biological equilibrium in the pond. The result is clear water in winter and no setback in early spring.
Some hobbyists connect their (koi-) pond to their own central heating equipment. Using a pump and a heat exchanger heated water is supplied to the pond. Pond heating in combination with isolating measures will prevent loss of heat. In winter many owners build a kind of tent over their pond from blister padding or synthetic canal plates.