The various options available to
the pond keeper as the winter approaches, fall into
two main categories:
Continuation of filtration.
Removal of filtration.
The decision is primarily determined
by comparing the benefits of continuing filtration,
which will help to sustain some degree of biological
colony and reduce the risk of the pond freezing over,
compared to the running cost and danger of low oxygen
due to freezing.
From a biological point of view,
the continuation of filtration in a heated pond is essential.
In an unheated pond, continuation will improve the speed
of biological maturation at the beginning of the following
season and give some protection in the event of winter
For winter running of unheated ponds,
here are a few tips to ensure that your fish have a
Gravity Fed System
If the inlet system is a Multi Level
Inlet, the bottom inlet should be closed off so water
is only drawn from the top of the pond. If a bottom
drain is being used, a reduction in the flow rate can
help to minimise the water temperature dropping.
Pump Fed System
Position the pump in the top third
of the pond and closer to the filter release point.
This will reduce the circulation and allow the bottom
of the pond to remain warmer.
Remember that returning water helps
to prevent the pond surface from freezing, which help
the oxygenation of the water. Therefore, the returning
water pipe(s) should release above the surface of the
pond (if the surface of the pond is moving, it will
freeze at a lower temperature).
If you have a waterfall, fountain
or venturi, they should be bypassed or switched off,
as the exposure of the water to the cold air, causes
a chilling effect which can be harmful to the fish.
You should switch off, drain and
remove the Ultra Violet Clarifier if there is any risk
of freezing. If the water is allowed to freeze inside
the UVC, the expansion of the ice will cause the quartz
tube to crack.
By leaving the filter system running
in the winter you will find that your filter will mature
quicker in the spring ready for the new season.
If severe weather is predicted, switch
off and drain the entire system (see Winter shut down
section for details).
As the purpose of heating a pond
during the winter is to maintain continuous summer conditions,
we advise that the filtration system be run as in the
summer months. However, the following are a couple of
points to ensure that all goes well:
If the heating system of the pond
should fail, the water temperature could fall rapidly,
which would be harmful to both the fish and the biological
colony. We therefore recommend that a backup heating
system is available.
If the filtration system is installed
above ground, try to insulate the outside of the filter
to avoid heat loss.
If there is any risk of the system
freezing, you should switch off, drain and remove the
Ultra Violet Clarifier. If the water is allowed to freeze
inside the UVC, the expansion of the ice will cause
the quartz tube to crack.
Avoid using waterfalls, fountains
and venturis as these will chill the pond. This will
increase the costs of heating and may also lead to areas
of the pond being at different temperatures.
If you wish to shut down the filter
systems during the winter months, we would recommend
The system should be left to run
for at least 2 weeks after feeding has stopped and restarted
approximately 3 weeks before feeding commences in the
Never feed your fish whilst the filter
is out of operation.
Once removed, the filter and UVC
should be thoroughly cleaned with tap water and stored
If removed, the pump should be cleaned
and stored indoors. If the pump is a Prima, it should
be kept in a bucket of clean water to prevent the seals
drying out and cracking.
If the entire system is removed,
we advise that a small pump is used to disturb the pond
surface or a floating pool heater is installed. This
is to try and prevent the pond from freezing over to
allow oxygenation of the water.
Whether the filtration system is
removed or run during the winter, it is a good idea
to do a little cleaning before the weather becomes too
bad. We would recommend the following:
The pond plants will start to die
off as the weather becomes colder, we would advise that
the plants be trimmed back to ensure that the dying
plants do not pollute the water.
During the season, the base of the
pond may have developed a layer of silt and sediment.
We recommend that this should be removed with the use
of a Cypri-Vac or similar device.
Please note that the above recommendations
are based on our experiences over the years and not
intended to be a definitive procedure or guide. Particular
care should be taken with small ponds, if moving water
is used to prevent freezing over, the chilling effect
is very hard to avoid. In this situation it may be safer
to shut down the filtration system and use an alternative
method of preventing freezing. If, however, you are
in any doubt as to what action to take during the winter,
consult your local specialist.