The weather definitely turns in October, with more rainfall and lots of leaves. If you have one, open the drain valve on your filter to purge excess water from the pond. Leave at least a 4” gap from the surface and the edge of the pond so that it doesn’t overflow with the next lot of rainfall.

Keep the pond cover net suspended tightly over the pond and not touching the water as if it does, leaves will be able to decay and herons will be able to reach and damage the fish through the net. Remove any leaves or berries that have got through with a net or via a pond vacuum cleaner. 

Clean the filter regularly, as you would do in spring and summer. The excess in organic matter from old pond plant leaves will rot if left in the filter, so clean the media and make sure no leaves or muck get stuck in there where they’ll break down and pollute the water over winter. Sponges can be replaced for new if you have other, mature sponges in operation or separate biological media. Remove any old filter bags filled with Barley straw or phosphate remover leftover from the summer.  

Pond water is usually clear at this time of year so you can turn off and decommission your UV. Old UV tubes should be disposed of as they will have run since March, and most are only at their best for six months of continuous use. Clean the quartz sleeve and maintain the seals and O rings if necessary. 

Feed the fish less often as water temperatures drop, and change to a winter diet like Wheatgerm. Use a pond thermometer or Seneye to monitor water temperature and feed Wheatgerm from 10-4C, and stop feeding below 4C. Invest now in a pond heater or ice prevention device as in unexpected cold spells, demand always outstrips supply. 

Check the fish for signs of damage or disease. They need to be full-bodied and healthy to survive a long, British winter and their immunity diminishes as temperatures drop. Colder water holds more oxygen so if your pond has a separate filter outlet that can still oxygenate the water, watercourses can be turned off as they will bring leaves down into the water and act as water chillers when the air gets cold.

If the pond has different water levels, move the filter pond pump up out of the deepest part of the pond so that the fish can sink down into the thermal layer at the bottom when the weather gets really cold. Remove all dirt and debris from the bottom of the pond as that will break down and produce noxious gases if the pond freezes over. 

Fish actually show their best colours at this time of year, and that’s why goldfish and koi shows are usually held in the Autumn. Make records of your fish numbers and their size, and take photographs for year-on-year comparison. Take one last time to enjoy the fruits of your labour before the winter shut-down.