We don't want to think about it just yet, but ahead of us is winter. We need to be ready for it so that your fish will have a stress free winter in their ponds. With luck they will get to be a ripe old age like our oldest koi who is now 28-9.
1) If you own vortex style filters, drain and clean them in Late Autumn , if your filters are the non vortex style of filtration give it a good clean
2) Make sure to renew air stones and cleaned the lattice work of jap matting.
3) Replace zeolite rocks with a charged bag of them putting the other bag on charge.
4) Replace lithaqua/crushed oyster shell and filter wool (batting).
5) Make sure to clean the bottom of the pond of detritus and dead leaves
6) Make sure you do water changes on a regular basis during the winter. You can do this by trickling in the water using the ambient temperature of the pond to warm the incoming trickle. If done correctly you will have no temperature change in the pond.
7) During fall net your pond against leaves twigs and other debris blown into your pond during high winds.
8) As the temperature of the air starts to dip going into winter it [where possible] it would be a good idea to cover the pond **
We have always used Polycarbonate Roofing Sheets to cover the pond against the worst that winter has to throw at it (you can buy double glazed lengths either new or second hand to fit the size of your pond) we use three over the pond.
** We also use this same type of sheeting to cover our filter housing
9) A good tip would be to buy a remote swimming pool thermometer to give you an idea of your ponds temperature during the winter .
10) Do routine water tests throughout the winter and act accordingly when action is needed by use of water change :- See 6)
11) As the temperature of the pond starts to dip below 10c stop feeding your fish until the spring. You should have been feeding a mixture of wheatgerm and Garlic from the start of fall .
12) Some koi keepers I know in Canada actually bring their fish indoors because of the horrific temperatures they get outdoors -24c with a windchill of -54c [we thought -10c was nippy].
13) Do daily visual checks on the pond throughout the winter .
14) Last but not least follow all of the above and your fish stand a very good chance of seeing the winter through unharmed