As soon as the last autumn leaves have fallen and the temperature really starts to drop, your perennial plant will die back and you won’t see them again until spring. This doesn’t mean that your garden maintenance jobs are over though, especially if you have a pond.
However, there can be some confusion over what to do with a pond over winter. Some people think it’s best just to leave it. After all, that’s what would happen in the wild. But this isn’t the case!
Below, we’ll take a look at some essential jobs you need to get done before the first frost hits. Doing these will help maintain the quality of your pond water, your pond plants, and any wildlife that calls your pond home.
1. Clean Your Pond
The first thing you need to do in order to prepare your pond for winter is clean it. Scoop out any fallen leaves and sludge that has fallen to the bottom and leave it on the side of your pond for 24 hours before composting it. This gives any tiny creatures a chance to crawl back into the water.
Once you’ve done this, add an animal-safe sludge treatment to the water. This will reduce the chances of any organic matter rotting at the bottom of your pond and affecting the pH.
2. Protect Your Pond Plants
Just like in-ground plants, pond plants need some protection over winter as well. Prune back any dead stems as this will stop them from decaying in the water and leeching pathogens that could harm fish and wildlife.
If you have any non-hardy aquatic plants in your pond, take them out of the water and bring them indoors. It’s a good idea to purchase a second-hand aquarium to store them in until they are ready to go back into the pond next spring.
It’s also a good idea to move any hardy aquatic plants to a deeper part of the pond. This will prevent the roots from freezing.
3. Cover Your Pond
There are two reasons why you should cover your pond with protective netting over winter. First of all, it stops any fallen leaves or other debris from getting into your pond and sinking to the bottom where it will rot.
Secondly, it acts as a barrier against predators that might try to prey on any fish you have in your pond.
The protective netting should be taut and held about 1-2” above the surface of the water. Hold it in place using surrounding rocks or peg it into the ground to stop it from sagging. Once spring has come around, you can remove the netting.
Can you leave fish in a pond over winter?
Since pond fish are cold-blooded animals, it is safe to leave them in your pond over winter. Their body temperature is controlled by their surroundings and, as such, they will behave in accordance with how cold or hot they are.
During winter when a fish’s body temperature is lower, their activity level will slow down, but they will be unlikely to die.
However, there are still some things that you need to do to make sure your fish are able to survive winter in a pond and reemerge in spring as healthily as possible.
The first thing you need to do is change what you’re feeding them. The colder water temperature will slow down their metabolism and their appetite, and they will struggle to digest their regular food properly.
Instead, switch to wheatgerm pellets as these are lower in protein and, as such, much easier to digest.
You also need to stop feeding your pond fish as soon as the temperature drops below 41ºF. When this happens, they are likely to go into a state of torpor, so any food you're putting in the pond will fall straight to the bottom and rot.
How deep should a pond be for fish to survive winter?
Another way you help your fish survive the winter months better is by making sure your pond is deep enough. This is because the lower they can go, the higher the temperature will be. However, the depth that you need will depend on the type of fish you have.
A pond with standard goldfish in it needs to be at least 2ft (60cm) deep. A koi pond should be at least 2-3ft (60-90cm) deep. If you live in an area that gets particularly bad winters with heavy snowfall and persistent frost, it’s a good idea to add an extra foot to the depth of your pond.
Should you break ice on a fish pond?
If you’ve headed outdoors on a winter morning to check on your pond and you’ve found the surface has frozen over, there will be an immediate temptation to break the ice. But is this the right thing to do?
Not necessarily. Pond animals (including fish) can survive cold temperatures and low oxygen levels, just as they would in the wild. They only start to suffer when there isn’t any oxygen in the water at all.
While a sheet of ice covering a pond can reduce the oxygen levels in the water, it won’t completely deplete them.
If you’re particularly concerned about ice forming on your pond over winter, you can float a tennis ball on the surface of the water. This will provide a hole in the ice that oxygen is able to get through when removed.
You can also add an oxygen pump to your pond which will constantly stir the water and increase the oxygen levels. However, if you’re going to do this you need to make sure that your pond is as clean as possible, otherwise, you may just be stirring up decaying organic matter.
To sum up, there isn’t any real need to break any ice covering a fish pond in winter. Your fish will be able to survive quite happily with the lower oxygen levels and, as the day warms up slightly, you may find that the ice naturally melts away by itself.