Winter season in garden ponds
Winter is a challenging time for most living organisms. They struggle to find food, have to brave the cold and conserve their energy as best they can to survive until the spring. The fish in our ponds also have to adapt to the sinking temperatures, and pond owners should ensure they are properly prepared for the inhospitable season. Find seven answers on seven questions dealing with winter time in garden ponds in our slideshow.
1. Can fish freeze and catch colds?

The body of a fish always has the same temperature as the surrounding water – which means, you’re your fish cannot freeze in the same way as you. That’s also why a fish cannot develop a fever.  The body cannot generate and maintain the rising temperature. In addition, fish have no lungs (and thus no bronchial tubes) from which they could and would have to cough up phlegm. Therefore, fish cannot catch the colds that we humans experience.

2. Do fish still tend to fall ill during winter?

There are diseases that fish may develop during the cold season in particular. Although illness will not necessarily occur in the winter, the fish are weakened by the end of the season, offering germs (as with many parasites) an easy target for the spring. At this time, fishes’ immune systems have not yet returned to full strength. 

3. Feeding fish in the winter?

It is a good idea to prepare fish for the winter via specific feeding in the autumn. Feed your fish for as long as they will eat – and are therefore not yet hibernating. When the temperature drops below 10°C, only feed special food which is easy for your fish to digest. Everything that the fish eat and digest should be used from now on will protect their energy reserves and fat reserves. 
Tetra Pond Wheatgerm Sticks

Specially developed floating food sticks for a healthy, balanced diet for pond fish when the water temperatures are cold in autumn and spring.
4. Do I need to bring my fish inside in winter?

No – fish can normally spend the winter in the pond provided it is deep enough. If they are well-conditioned for the winter, ‘normal’ pond fish such as koi, goldfish and orfe will have no problems with low temperatures. Only highly-bred goldfish varieties such as ryukins may have to spend the winter in an aquarium. However, make sure to bring the fish indoors at an early stage rather than waiting until it turns cold.

5. Can fish freeze in the ice?

To ensure that your fish survive the winter unscathed, your pond must be of an adequate depth. A healthy fish will always hibernate in the deepest part of the pond and will not come into contact with the ice. The colder it gets where you live, the deeper the pond should be. Otherwise, there is a danger that the water may freeze right down to the bottom in very cold winters. 
6. Will the fish be in danger if the pond surface completely freezes over?

If your pond is well maintained, there is no need to worry if the surface of the water freezes. If, however, the pond is poorly maintained and full of mulm, it may prove dangerous to its occupants. Why? Oxygen may become scarce in the water and fermentation gases may develop that cannot be removed. If a pond is well maintained this would only become a problem after a very long period of ice. Otherwise, a layer of ice on the water presents no danger. 

7. Can I hack holes in the sealed ice surface?

Fish have very good hearing: If you hack a hole in the ice or even just walk around on the ice, it is very loud for your fish and they would try to flee. But as they are hibernating and therefore in a form of energy-saving mode, it is impossible for them to escape. However, their instinct would be to try it anyway, leading them to ‘have a breakdown’. If you need to make a hole in the ice, do it ‘quietly’ using hot water. 

AUTHOR: Tetra GmbH
DATE: 23.11.2016