Autumn is the time to make sure that your pond, and in particular the fish in it are fit to survive the winter.

Water & Plants

The first task as autumn approaches and the winter nights start to draw in, is to cut back any dead and dying foliage from marginal plants and lilies. Most plants can be left in position in their containers, but more delicate marginal plants are best moved to the deeper parts of the pond for winter. Here they will avoid the worst affects of the frosts, and be ready to spring back to life when returned to the margins once those frosts have passed.

Any sludge, sediment or other rotting organic matter should be removed from the bottom of the pond. There are various was in which this can be achieved, syphons, long handled nets and pond vacuum cleaners such as the "Oase Pondovac" . However for small to medium sized ponds it is often easiest to transfer all the plants and most of the water to a separate container such as a child's padding pool. If you have a pond pump, this can be used to pump the water, otherwise place the paddling pool next to the pond, and you may surprise yourself with how quickly you manage to bucket the water from one to the other.

Try to keep as much of the original water as possible, this is the water the fish are used to and it is far preferable to tap water or even rainwater. When refilling the pond use a good quality water dechlorinator to treat any new water you add to the pool.

Don't Overfeed

As the weather cools, fish become less active and their metabolism slows, they become less able to digest their food and therefore eat less. In Autumn and again in spring we recommend the use of "Wheatgerm" foods. At lower temperatures fish find wheatgerm foods more digestible than the higher protein foods usually fed in Summer. Once the pond temperature falls below about 55 degrees Farenheit 12 degrees Centigrade stop feeding altogether as fish can not digest food at all at these low temperatures.

Pumps & Filters

During the Summer months pond filters should be run 24 hours a day. Come the Winter, many people choose to turn off their filters and if you do, make sure that all the media is thoroughly washed and stored dry. In the Spring when you start the filter running again it will take about 6 weeks to become fully active, during this time turn off any UV units you have as they will hinder the establishment of the beneficial filter bacteria.

Alternatively it is OK to leave your pump and filter running throughout the winter, although the filter bacteria will be fairly inactive due to the low temperatures, as the weather starts to warm up in the spring, the bacteria will be there waiting to "spring" into action.

If you do leave your filter running throughout the Winter, do take care to ensure that it is protected from the worst frosts and won't freeze solid or overflow.

If the pump is turned off during the winter, either remove it from the pond and thoroughly clean it before dry storage or place it at the bottom of the pond (where it is not going to freeze solid). In this case make sure you run it for a few minutes at least once a week. This will prevent the bearings from becoming seized.

Ice

In a still pond different temperature water can form different layers. In a pond with ice on the surface the warmest spot will be the bottom of the pool where the water will be 4 C (39F). The fish will shelter in this warmer water.

A layer of ice on a pond will prevent the exchange of gases between the air and water. Respiration of the fish & rotting organic matter will cause oxygen levels to fall and carbon dioxide levels to rise in the pond. There is a danger that this could ultimately cause the fish to suffocate. One way to prevent this from happening is simply to use a pond pump to circulate water and help keep an area free of ice. If you use this method, take care not to disturb the water at the bottom of the pond too much. If this does happen the water temperate at the bottom can drop below 4 degrees centigrade 39 degrees farenheit which can be stressful to the fish. It is therefore best to position the pump sufficiently deep in the water that there is no risk of it freezing solid, but sufficiently shallow that the water at the bottom is not disturbed.

some people use a floating ball or similar to keep an area of the pond free of ice. Frankly, this is pointless, once frozen in it will, like the ice, prevent gas exchange.

If your pond does become frozen for any prolonged period it is essential that you find some way of making a hole in the ice. DO NOT try to smash the ice, this can send shock waves through the water which can stun and kill fish. Instead stand a pan of boiling water on the ice to melt a hole. Once melted keep it free with more boiling water or better still there are a number of products which can be used to help keep an area in the pool free of ice for gas exchange. These include pond heaters, and polystyrene foam floats, the latter are cunningly designed to provide insulation whilst still allowing air to circulate.