Essential Pond Maintenance for Autumn

Updated: Oct 18, 2021

Autumn has crept up on us very quickly here at Keruto Koi, so we wanted to share our top tips for maintaining your pond through autumn so as to prepare your fish best for the rapidly approaching winter season!


Always ensure that when your hands are in your ponds, you are wearing long gloves, ideally elbow-length, so that no toxins from your hands can enter the water.


Plant and Vegetation Maintenance

Upkeep of your pond is important all year round, but autumn can bring some extra work with it. One important autumn job at Keruto Koi is to remove any leaves from the ponds that have fallen off the surrounding trees and it is something you will need to do as well if you have any trees around your ponds. Not only does it improve the look of the pond and the viewing of your koi fish when you remove any fallen leaves, but some leaves, such as oak, can also be toxic to fish and upset your water parameters, so it is very important to remove leaves from your ponds as quickly as possible.


When it comes to removing leaves, all you need is a good net with a long handle, but if removing leaves becomes a job you need to do frequently, you could consider covering your pond with a net or a lid for autumn and winter. Both a net and a lid would be a barrier to watching your lovely fish but they each have other benefits to be considered. A net will also be beneficial to protect against pests targeting your koi and a lid can help insulate your ponds in the winter.


As well as removing dead vegetation from surrounding plants that fall into your ponds, you should make sure to check any plants that are growing in your pond if you have them. Most plants will have had a good season of growing over the summer, so you need to make sure to trim them regularly to keep them looking tidy. The best time of year to do any major trimming or cutting is in autumn as the cutting process can make the plants a little more vulnerable but the plant still has time before winter to recover. If you trim your plants earlier in the year, they will likely still be unkempt and messy by the end of summer as this is the season when they do most of their growing.


It is important to ensure that all the plants growing in your pond itself are beneficial to the water and the koi fish and that your pond hasn’t picked up any dangerous weeds. Most aquatic plants are fine to keep in ponds and are in fact very useful to the life within the ponds. Plants will provide oxygenation and help maintain water parameters such as nitrates so that you will need to do water changes on your pond less frequently. That being said, there are still some plants that can be harmful to your koi, and it is important to check that you know what every plant in your pond is and that they are not harmful to fish. The most dangerous plants to koi fish include yew, aloe, cardinal flowers, and oleanders.


Pond Base Cleaning


One of the dirtiest parts of a pond is the base where organic waste from the fish can build up on the bottom of a pond to form a thick pond sludge. Not only does this pond sludge not look very nice to anyone enjoying your pond, but it can also smell very foul if your water parameters are not absolutely perfect. A very small amount of excess nitrates or nitrites are an indication that your pond needs a water change but they will also cause any pond sludge to smell like rotten eggs!


When it comes to cleaning your pond, you should only need to completely empty the pond if the sludge is more than 3-4 inches thick or you have a bottom drain that is either blocked or broken. Otherwise, you can just remove the same amount you normally would for a water change.


For smaller ponds, you can then use a net to scoop out as much sludge as possible. A net is not recommended but it is a good alternative to koi keepers on a budget. You will need to take care to not disturb the sludge into the water too much as this can disturb and damage your koi fish. A pond vacuum will remove a lot more than a net ever could and is much quicker and easier to use. For a large pond, a pond vacuum is an essential piece of kit!


If you have any non-aquatic plants or vegetables, the sludge removed from your pond is a great fertiliser for these!


Preparing for Winter


Over the colder months, you may notice some changes in your koi’s behaviour. Typically, koi carp will go into a type of hibernation called torpor in the winter. In this type of hibernation, the koi will appear to be sleeping most of the time, but they are actually just slowing all their behaviours down. In this state, they will be able to save energy by lowering their body temperatures and reducing all of their primary body functions, such as metabolism and breathing. This all allows the koi to survive the potentially freezing weather of the winter months.


During this time of torpor, the koi will not need to eat food and will likely not want to, either. Therefore, it is worth considering changing their food to one that will help them to build their fat stores in preparation for hibernation so that they have a better chance of staying healthy during the tougher weather.


You may also notice that your koi are eating more of their food throughout autumn, and this is their bodies way of preparing for winter and building up their fat stores. During this time of year, it can be worth checking your fish a few extra times a day and feeding them as much as they will eat. We recommend feeding small amounts often so that you are not underfeeding but also not overloading your filtration system with lots of uneaten food.



Hopefully, you are now ready to clean your pond and prepare it, and your fish, for winter. By preparing properly now, you can be sure that in the springtime, your pond and your fish will look as nice and healthy as possible!


Keep an eye out as we will be back soon with more information and advice for looking after your pond and your koi fish over the winter months.

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