As 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.
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 sterilizers 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.