It’s s-no-w surprise to me

Here’s the text of the press release we put out on Friday alerting people not to worry too much about the icy pond conditions.

The pond above is one I’ll return to – it’s at a school in Abingdon and seems to have all the features needed to provide a good natural oxygen supply.


POND CONSERVATION PRESS RELEASE 9 JAN 2010: Should I break the ice on my pond to protect its wildlife?

Many of Britain’s 3 million garden pond owners will be wondering whether they should break the ice on their ponds to protect wildlife.

Standard advice has always been that, to safeguard garden pond wildlife during freezing weather, you need to make a hole in the ice to ‘allow oxygen into the pond’.

But new research undertaken by Pond Conservation suggests that most garden ponds and their wildlife will be OK during the big freeze if just left to their own devices.

And most surprising of all, if ponds have clear water and plenty of pond weeds, oxygen levels can actually go up during the freeze – the exact opposite of what is traditionally believed.

Why does this happen? Even under ice, plants continue to photosynthesis, producing oxygen. With a covering of ice the oxygen is trapped in the pond and, if the ice cover lasts for long enough, oxygen levels will rise.

So if garden ponds have lots of underwater plants or algae, oxygen levels can nearly double in the coldest weather.

So what should people do to look after their ponds?

– Don’t worry too much. Your pond is unlikely to freeze solid, and there’s a good chance it will have enough oxygen for the animals in the pond – dragonflies, damselflies, mayflies, water beetles, hibernating frogs and the rest – to survive.

– Don’t bother to make a hole in the ice: there’s little evidence this makes any difference to the amount of oxygen in the pond. This is because oxygen diffuses so slowly into still water – about 2 millimetres a day! – so it takes over 6 months for oxygen to diffuse to the bottom of a 50 cm deep pond.

– If there is lots of sediment or leaves in the bottom of the pond – and you also have fish – you do need to get oxygen into the pond. To do this you need to stir the water in some way so that de-oxygenated water is constantly brought into contact with the air. Running a pump or fountain, if you have one, should do the trick.

– If the pond is covered with snow, brush as much snow off as possible. Snow blocks the light and will stop underwater plants from producing oxygen. In these conditions, oxygen levels can go down a lot. BUT SAFTY FIRST – TAKE GREAT CARE NOT TO STEP ONTO THE POND ICE IN CASE YOU BREAK THROUGH.

Dr Jeremy Biggs of Pond Conservation said: “In the longer term – if you want to make a pond that will naturally maintain high oxygen levels in winter, make sure that the pond has plenty of underwater plants (even algae will do), and is shallow (around 20-30 cm maximum depth is good). Shallow ponds are better lit than deep dark ponds so can produce more oxygen for their volume. Ideally, also keep the pond water as clean and unpolluted as you can to help the submerged plants flourish”.


2 Responses to “It’s s-no-w surprise to me”

  1. JM Says:

    We have a smallish but deep pond ( 31 inches max) which has a series of shelved areas in the margins so that approximately half of the surface of the pond is covered by plants in summer. We also have some oxygenators submerged growing in the pond. We use a biological/ mechanical filter + water fall (spill stone) and because of the balance between fish/ plants/ wildlife we have few problems with maintaining the pond. Seldom have any trouble with algae and temperature is never a problem in summer. Shallow ponds are not always ideal if they heatup in the summer and imbalance causes nitrate/ nitrite /algae build ups and reduced oxygentation. Currently our pond has 5 inches of ice on top and the fish are just fine.
    The ideal is not a shallow pond but one which has a shelves, a bit of a deeper area, some oxygenating factors and enough plant life as in natural ponds.

  2. Should I break the ice on my pond? The answers. « The Garden Pond Blog Says:


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