As the cold weather draws nearer we start to worry about how our fish will survive the harsh winter months.
The truth is pond fish are very hardy and usually have no problem getting through the winter, but there are things we can do to help them along.
There are two things that you can do to help your fish get through the worst of winter, use an aerator and add a de-icer.
Why do pond fish die in winter
There are two reasons why fish die in the winter, lack of oxygen and the build up of toxins in the pond water.
As the colder weather approaches pond fish will start going into a semi-hibernation state, this is normal and usually starts when the water temperature of your pond drops below 55 degrees.
Once your fish are in their semi-hibernation state you should stop feeding them, this is for two reasons, firstly your fishes digestion system which also slows down won’t be able to cope with the food and secondly any food that is not eaten will sink to the bottom of your pond where it breaks down, as it decomposes it releases ammonia.
This along with fish waste (poo) and organic matter also decomposes and produces ammonia which is bad for your fish, the ammonia breaks down into nitrites and nitrates, the nitrates are very toxic to your fish and is one of the causes of fish death not just in winter but all year round.
As winter takes hold there is a possibility that the pond will freeze over, if it does the poisonous toxins in the pond water will not be able to escape, your fish are now trapped in a sealed pond full of poisonous water, unfortunately this could lead to fish dying.
If you can it’s a good idea to clean your pond before winter, this will the remove organic waste that could cause problems as winter hits.
The second cause of fish death during the winter months is lack of oxygen, in your pond you will have beneficial bacteria, these are good, they eat up the ammonia, the problem is they also use up oxygen which leaves less oxygen for your fish, you also have plants that are also competing with depleting oxygen supplies.
Again if your pond freezes over there is no way to get any extra oxygen into your pond.
How you can help your fish during winter
As I said at the start of this article you need to use an aerator, I believe this is one of the best ways to prevent fish loss during the winter months.
An aerator uses air stones to produce air bubbles, these bubbles allow more oxygen to enter your pond.
With more oxygen getting into your pond your fish, plants and beneficial bacteria will have enough to share, keeping your fish alive.
I also mentioned the use of a de-icer, the purpose of a de-icer is to keep an area of your pond open, it does this by gently heating the surrounding water, this leaves a nice hole were toxins can escape.
Don’t think a de-icer is a liquid you spray on to your pond like you would your car windscreen, this is a floating heater purposely made for ponds.
I have heard of people trying to break open the ice by whacking it with all sorts of implements, this is a no no, the shock of all that banging can kill fish.
If you haven’t yet bought a de-icer I suggest you do, in the meantime you could fill up a bowl of hot water and place it gently on the ice to melt it, obviously this will only be a temporary solution.
If you have an aerator running it is possible that this will be enough to keep a hole in any ice that covers your pond, but for piece of mind I would run a de-icer and aerator together.
One thing I haven’t talked about yet is the depth of your pond, if you have a shallow pond your fish will have a hard time during the winter, your fish need to go to deeper water where it’s a bit warmer and less chance of freezing.
If this is a problem you could look at inline pond heaters, these will turn on when the temperature drops to a certain level, they only warm up your pond very slowly, so they shouldn’t affect your fish.