How to take care of your pond fish in winter?

Winter is coming, temperatures are starting to drop, and the first to suffer are the people in your garden pond. What can you do to help them get through the winter?

Bringing your pond fish indoors

Bringing your fish indoors in winter can be a good solution, especially when :

  • Your pond is less than 60 cm deep
  • Your pool is located in a patio or a courtyard

You can then transfer your fish to a large tank, left for example in your garage or basement. For the fish to go into hibernation, the water must not freeze, and ideally the water temperature must be above 10°C. Since the fish will go into hibernation, they should not be fed. On the other hand, water circulation should be important.

You can also transfer your fish in the house: tank, aquarium, children’s pool. It is important to make sure that the water is well renewed to avoid the accumulation of waste. Also pay attention to the temperature and light, which must not be excessive.

Leaving your fish in your outdoor pond

Water quality and maintenance
In winter, it is even more important to look after the quality of the water in your pond. Optimal water has the following characteristics: pH = 7-8, nitrite = 0.15 mg/L, nitrate = 0.50 mg/L, ammonia = 0.15 mg/L.

It is therefore essential to test your pond water before winter comes. If the water has a quality defect, certain acidic or basic chemicals can be added to the water. In addition, in winter, bacteria that are useful for maintaining water quality have reduced activity due to the drop in temperature. There are also solutions containing bacteria or enzymes, for example, to limit the growth of algae.

Pay close attention to the presence of leaves or waste in your pond. If possible, come by once a day and remove the residue with a net. You can also place a net over your pond. The net has two uses: on the one hand, it prevents leaves from falling into the water; on the other hand, it limits attacks by cats and birds, to which fish are very sensitive, especially during the winter hibernation period. On the other hand, you can leave a pile of leaves at the bottom of the pond, they can provide shelter for the fish.

Before winter, it is best to clean pumps and filters in your pond and make sure they are in good working order. For cleaning, simply use water, without detergents. It is recommended to disconnect pumps and filters and store them in a dry and cool place. It is useful to use a secondary pump, known as a winter pump, adapted to low temperatures or even freezing temperatures.

Feeding the fish
It is recommended that the water be renewed by at least 20%. Do not hesitate to add water if necessary, the optimal depth being 1 meter.

Frost prevention
It is possible to heat the water: in winter, the ideal temperature for fish is 8 to 10°C. At this temperature, hibernation is not complete: the fish are said to be resting, they need to be fed a little.

If you do not heat the water, several solutions exist to avoid ice formation. All of them rely on sufficient aeration of the pond :

  • You can use an air pump, which will have two roles: it will firstly bring oxygen to the fish; it will also create air turbulence, which will avoid the formation of an ice layer. The kit should be placed halfway up the pond: if you place it too deep, the warmer water at the bottom of the pond will be stirred, which will bring the fish out of hibernation.
  • You can also use an air stone with an indoor/outdoor air pump. The air stone should be placed in a corner of the pond, just below the water surface. The air pump can be placed in the house and connected to the air stone by a hose.

To limit the ice surface in the pond, you can put a plastic bottle in the pond; slightly weighted, it will keep the area free of ice and thus preserve the oxygen supply for the fish. You can also place a bundle of wood or straw in the water to keep an area free of ice.

Warning: if a layer of ice is formed, do not break it! This would generate waves that can hurt the fish! Moreover, the fish would panic and consume more oxygen. If a layer of ice has already formed, put a container of hot water in contact with the ice layer and wait for it to melt. You can also pump water, and thus create a 2-3cm layer of air, which will protect the pond.