Autumn Pond MaintenanceAs the days begin to shorten and summer slowly slips into autumn, just like the rest of the garden, there are a few seasonal jobs to be done around the pond to start to prepare it for the eventual onset of winter. Plants, fish and equipment all have their individual needs at this time of the year and – with British weather being so unpredictable – it is as well not to leave starting on the work too late, in case an unexpected cold snap catches you out. Year round pond maintenance is important, and we have guides for Spring. Autumn, Summer and Winter

Pruning and Feeding

After the growth of the summer, by the end of September the pond plants will be starting to die back in readiness to over-winter. As soon as this begins to happen, start to remove their dead leaves and cut back the marginal plants to stop too much organic material collecting in the pond and then decaying in the water. This is particularly important for the smaller pond, though even a relatively large garden pond can accumulate significant levels of rotting vegetation if this seasonal pruning is overlooked.

For the same reason, any tree leaves falling into the pond should be removed; some people install a fine nylon net over the surface, either permanently or as a temporary measure, to make the job easier. Finally on the plant side, as the risk of frost increases, any in or around the pond that are not fully hardy should be either removed to a safe place, or covered in horticultural fleece, as appropriate.

At this time of year, the fish in the pond will be preparing to over-winter, so as the water temperature begins to drop, it is a good idea to begin feeding a lower protein diet, until they eventually stop feeding altogether as autumn progresses. Although they will happily keep eating the summer’s high protein fodder throughout this period, as they wind down to winter dormancy, being cold-blooded, their ability to digest and make full use of it reduces as the temperature falls.

Food that is not fully digested will tend to contaminate the water and poor water quality is often a big factor in making fish more prone to disease – so switching feed is always a prudent move.

Although the ornamental strains of the carp family commonly kept – a group which includes not only koi but also goldfish, shubunkins koi, orfe and rudd – are not so robust as their wild ancestors, with a little help they should make it through the winter in good health.

Cleaning and Maintenance

As plant and fish activity slows down, the pumps and filters that have helped keep the pond a balanced and healthy environment throughout the spring and summer can gradually stand down too. The flow through the filters can be reduced from the beginning of autumn and by the time the water temperature has fallen to around 10 degrees C, UV sterilisers can safely be switched off and filters disconnected and cleaned for when they are next needed.

Some pond-keepers prefer to lift pumps during the late autumn, to leave the deeper parts of the pond – where the fish will be hiding – undisturbed. This also provides a good opportunity to clean the intake and filters thoroughly and check for any signs of wear.

The final major autumn job is to check the water quality. Even the best filtered pond can gradually accumulate unwanted chemicals – particularly nitrates – which are not ideal for fish to languish in over the winter months and may drive an early algal bloom in the spring if something is not done about them. There are many brands of simple nitrate test kits on sale which will very quickly show if there is a problem and highlight if any action is needed.

For any gardener, autumn is a strange time, standing between the fading glories of one growing season and the promise of the next and the water gardener is no different in this respect. There is always a slight tinge of sadness as the days draw in and nature slowly winds down towards winter, but if we use this time wisely to carry out a little maintenance, we can be sure that come next spring, our water feature will get the best chance to shine once again.

Top Autumn Pond Tasks

Cover your pond with a net to prevent leaves and debris from falling in

Autumn is the time of the year when the trees begin to shed their leaves, and these leaves can quickly accumulate in your pond. Leaves can cause a drop in the water quality, as they decompose and release nutrients into the water, leading to algae blooms and other water quality issues. Installing a net over your pond is a simple and effective way to prevent leaves and other debris from entering the pond. The net should be secured tightly over the pond to prevent any gaps or holes through which leaves or debris can enter.

Prune back any foliage that hangs over the pond to reduce the amount of debris

Foliage hanging over the pond can drop leaves and debris into the water, causing the pond to become dirty and unhealthy. Pruning back any foliage hanging over the pond will help reduce the amount of debris that falls into the pond. Trim back any overhanging branches, bushes or trees that might cause excess debris to fall into the pond. It is best to remove any foliage that is within a few feet of the pond to prevent leaves and debris from falling in.

Use a skimmer net to remove any floating debris from the surface

Autumn is a time of the year when debris accumulates quickly on the surface of the pond. Fallen leaves, twigs, and other debris can clog filters and lead to poor water quality. Use a skimmer net to remove any floating debris from the surface of the pond. A skimmer net is a fine mesh net on the end of a long pole that you can use to remove debris from the surface of the water. Regular skimming of the surface of the pond will help keep the water clean and clear.

Remove any sludge that has accumulated at the bottom of your pond using a net and gloves or a pond vacuum

Over time, debris and organic matter will settle at the bottom of the pond, forming a layer of sludge. This sludge can contain harmful bacteria and other contaminants that can negatively affect the health of your fish. Remove any sludge that has accumulated at the bottom of your pond using a net and gloves or a pond vacuum. If you are using a net and gloves, gently scoop up the sludge from the bottom of the pond and dispose of it away from the pond. Alternatively, a pond vacuum can be used to suck up the sludge from the bottom of the pond.

Test water quality regularly to ensure the parameters remain within acceptable levels

Autumn is a critical time to test water quality regularly to ensure that the pond’s water parameters remain within acceptable levels. As temperatures begin to drop, the pond’s biological activity will slow down, reducing the effectiveness of the filtration system. This slowdown can lead to a buildup of ammonia, nitrite, and nitrate, which can be harmful to fish. Regularly testing water quality will help identify any imbalances and allow for prompt adjustments to prevent any health issues with your fish. Test water quality parameters such as pH, ammonia, nitrite, nitrate, and alkalinity at least once a week to ensure your pond remains healthy.

Consider adding beneficial bacteria to break down organic material and reduce the risk of winter fish kills:

As temperatures drop, beneficial bacteria become less active in breaking down organic material in your pond, which can lead to a buildup of harmful toxins. By adding beneficial bacteria to your pond, you can help ensure that the organic material in your pond is broken down and that harmful toxins are eliminated. This can also help prevent winter fish kills, which can occur when too many toxins build up in the water.

Reduce the amount of food you feed your fish as their metabolism slows down in colder temperatures:

Fish have a slower metabolism in colder temperatures, so they require less food. Overfeeding your fish in colder temperatures can lead to digestive problems, which can be fatal for your fish. It’s important to gradually reduce the amount of food you feed your fish as the temperature drops.

Monitor the water temperature and stop feeding your fish altogether once it reaches 50°F:

Once the water temperature drops to 50°F or below, you should stop feeding your fish altogether. Fish become less active and their metabolism slows down significantly in colder temperatures, which means they require very little food to survive.

Turn off waterfalls and fountains once the temperature drops below 40°F to prevent damage to your equipment:

Waterfalls and fountains can cause damage to your equipment if they are left on when the temperature drops below 40°F. Water can freeze in the plumbing and cause cracks in your pipes or other equipment. It’s important to turn off waterfalls and fountains and drain any excess water from the pipes to prevent damage.

Check your equipment and make any necessary repairs before the winter months set in:

Before winter sets in, it’s important to check all your equipment to ensure it’s in good working order. This includes your pumps, filters, and heaters. Make any necessary repairs or replacements to ensure that your equipment is functioning properly before winter sets in. This will help prevent equipment failures during the winter months when it’s more difficult to make repairs.


Autumn is a critical time to prepare your pond and fish for the colder winter months. Leaves and debris can accumulate quickly, which can lead to poor water quality and health issues for your fish. It’s important to cover your pond with a net, prune back any foliage, and remove any sludge or debris that has accumulated. Regularly testing water quality parameters and adding beneficial bacteria can help prevent winter fish kills. As the temperature drops, it’s important to reduce the amount of food you feed your fish and stop feeding them altogether once the temperature reaches 50°F. Turning off waterfalls and fountains and checking your equipment for repairs before winter sets in will help prevent equipment failures during the winter months.


Last Modified: April 6, 2023