Winter Pond Care

My Winter Pond in the deep freeze

There isn’t a great deal for the pond keeper to do in the winter months, except sit and wait out the winter. There are a few duties however, still required to ensure that the pond and its pondlfe get the best chance of making it to Spring.

Firstly, I think you should have a good quality strong net over your pond for winter. Whether your pond is shallow like mine, or just to catch the last of the Autumn leaves. Fish tend to hang about at the bottom of the pond in a bit of a stupor. So even in a deep pond, a net is an extra security measure.

I use a Clearview nylon net which affords enough protection but doesn’t spoil the view.

All my fish disappeared without a trace in Winter 2010 and when I spoke to a fellow Pond keeper they said it could have been Mink from a nearby river. It did get me thinking and I do live close to a river – so who knows.

Anyway, I want my pond as secure as possible over the Winter just to ensure that no hungry Heron thinks it can stop by for a bit of fastfood.

The main area of concern in Winter for Pondkeepers is : what to do if and when the pond freezes over.

First off, the Pond will never freeze right to the bottom (in the UK) so most hardy Koi and Goldfish will be ok, even during the big UK freeze of 2010 with temperatures dropping to -17c, it didn’t freeze right down to the bottom of my pond, which is only 2and a half foot deep in the deep end.


There are many opinions about whether it is advisable to leave your pond pump running during the winter months – or not.

Advocates against say that there is an obvious saving to be made in electricity and this can increase the life of the pump by giving it a winter break. Coupled with this is the reduction in algae and blanket weed growth in winter due to colder temperatures and less sunlight so the filter is not required to cleanse the water as much.

In general though, I would say it is advisable to keep the pump running in winter, albeit in a reduced capacity than in the warmer months for as long as possible.

Some pumps come with the ability to control multiple water features. Such as a water fall feature and separate statue water features. It is best to run only some of the water features rather than all.

Not only will keeping at least one of the water features going as long as possible introduce oxygen into the pond, it will keep the water on the surface circulating and this has the added benefit of helping prevent the pond icing over as quickly, when the temperature does drops.

Another benefit of running the pump as long as possible is the reduction of nitrogen in the pond. Nitrogen buildup happens naturally due to the rotting matter which decays in the bottom of the pond. Nitrogen buildup can be bad news for health of any resident fish population. A pump helps remove this nitrogen and recycles the water replenishing it with oxygen.

If your pump has a UV filter definately turn this off, it would be good practice to take out the bulb aswell and save it for spring. As mentioned above, algae and blanket weed does not present as much of a problem in winter and running the UV filter through winter will only decrease the life of the bulb.

That said, there comes a time when turning the pump off is a must. Namely, when the pond starts to freeze over and the circulating water is no longer keeping it at bay (probably around -10c in Northern UK climbs). If the pump or the pipes start to freeze whilst running, this will inevitably increase the pressure on the pump and may result in a burst (not good).

It is advisable to ensure that when the pump is turned off, a hole is kept in the ice to allow release of nitrogen from the pond, to escape. Their are two methods you can use, I employ both :

A tennis ball allowed to float freely disrupts ice buildup (to a point)

And/or

A boiled kettle poured continuously onto one spot, which is the best way to gently melt the ice, to create a blowhole. Never break ice forcefully, as it can create soundwaves which can stun or kill your fish.

Lastly, the decision to switch off the pump or leave it running during winter is down to the pond owners own experience – and most importantly, the climate they live in.

I would say from my own experience of a Northern UK climate that the overriding benefit to keeping the pump running (aslong as possible), is a delay in icing over and the continued oxygen to the fish.

You really just need to decide early on whether you want to turn the pump off at the beginning of Winter, or like me – keep it going until the freeze really sets in.

So bar watching for the ice buildup, there isn’t much else for you to except sit back and plan your big Spring pond clean out and what new plants and fish you may want to add.

Update’s

December 2011 Update – With such a mild winter this year in Northern UK, my pond has only threatened to ice over once in December so far but I kept the pump going right through. With temperatures much milder (but way above 5c cutoff point) than 2010, I started feeding my fish again infrequently in January 2012, with very small portions as they have became active. But if the temperatures drop again I will stop, its the keepers call but base your decision to feed or not on the ‘5c’ rule and not the season.

December 2012 Update – Its December now and we are getting down to -5c but I still have the pump going as the movement water is stopping the pond freezing over fully. I’ll keep monitoring it and when the temp drops further, the pump will be off and out of the pond, till Spring.

January 2013 Update – This year I decided to remove the pump after the first freeze and let the pond freeze over. I periodically venture out with a boiled kettle and melt a blow hole, other than that- nothing. All of my fish are fine.

December 2013 Update – Its been another mild one for Northern UK and I have kept the pump running throughout. There has been no hint of freeze yet.

Spring Pond Care
Summer Autumn
Pond Care

  • Chris

    I would advise people to keep their pond pump running during the winter as in the winter of 2010 I lost almost all my fish due to the pond being frozen for such a long period. I have a 100,000 liter pond that we use not only for fish but also to swim in. it is 8’6″ at the deep end and 5’6″ at the shallow end with large beds planted with aquatic plants to filter the water. I always used to keep the pumps running during the winter, however due to pressure to reduce our electric bill I turned the pumps off during the winters of 2009 and 2010. In 2009 the fish were ok but as I said I lost almost all of them in 2010. My local aquatics center said this would be due to toxic gasses trapped by the ice poisoning my fish, from now on my pump will remain running through the winter. Hope this helps Thanks Chris