What happens when your pond freezes over?

When we experience freezing temperatures in Ireland in the Winter and ice begins to form on the surface of your pond, in most circumstances, it will still allow gasses to be exchanged. Oxygen will still be absorbed from the air and Ammonia will still be released; this process will just be slowed down drastically. If your pond is ornamental with no fish, you don’t have to do anything to your pond unless you feel the need to do so.

Cold water, typically, has plenty of dissolved oxygen present, and during the winter months fish and wildlife will use up less oxygen. As a result, most aquatic wildlife will be perfectly fine if the pond freezes over for a couple of days. However, if ice forms for more than a couple of days, you will need to take action in order to save your fish!

When ice develops and freezes the pond surface for more than a couple of days, the oxygen levels will start to fall, and gases will build up in the water, these gases will build up under the ice and become trapped in the pond. This will prove to be fatal to your aquatic life, especially for a heavily stocked pond or in cases where there is a lot of debris in the pond.

The first step to keeping your fish happy if the pond is already frozen is to break a hole in the ice. This will allow for the exchange of gases to resume and will eliminate the build up of dangerous gases which will cause harm to your fish, just remember, try causing as little disruption to the water as possible when breaking the ice as any shock waves you create may stress the fish out further. As tempting as it may be, NEVER pour boiling water onto the ice, this will only result in additional problems for your fish!

Despite the above, the best method when dealing with plummeting temperatures is to ensure your pond doesn’t freeze over at all. There are a couple of methods available for doing this.

1. Keep your pump running – This circulates the water and prevents ice forming. Try to keep the pump away from fish and below the ice levels of your pond. You do not need to filter your water as waste is at a minimum during winter. All our Oase pumps are designed to withstand freezing temperatures up to -20°C.
2. Keep an Aerator switched on – The air pump displaces water and forces it to move, preventing the surface from icing over. Just like a normal pump
3. Get a De-Icer– These are often small, inexpensive floating heaters which keep the water hot enough to prevent ice from forming.

We hope this has cleared things up, but as always, please don’t hesitate to contact us if you have any further questions.