Should I break the ice?

This winter’s cold weather naturally prompts many people to ask: ‘Should I break the ice on my pond?’.

Most advisors say you should make a hole to let oxygen in or ‘toxic gases’ out.

So last year, when I measured what actually happened in my pond when it iced over, it was a bit of a surprise to find that oxygen levels nearly doubled when the pond was frozen.

Far from causing a shortage of oxygen, ice cover made oxygen superabundant.

This was because photosynthesis continued under the ice but the oxygen could no longer escape to the atmosphere. So far from threatening wildlife, ice cover made certain there was no oxygen shortage.

So now this year’s freeze is a good opportunity to see whether the same thing happens again: the only difference is, this time I’ve got two ponds!

So what is happening?

Both ponds have been frozen now for 5 days – I began measuring oxygen on the third day.

The picture shows oxygen levels slowly rising in the old pond and staying pretty much constant in the new pond.

Why the difference? I’m not completely sure but there are dense growths of mosses growing under the water in the old pond. The new pond so far has only the algae growing on the bottom sediments and in the water.

So far neither pond is showing any signs of oxygen depletion following ice cover.


2 Responses to “Should I break the ice?”

  1. John Greenwood Says:

    Fascinating information Jeremy. I had always suspected it was better to leave the surface ice but my wife wants to make the hole with hot water to release the gases!
    Will you be making a test hole in one of the ponds to see if the oxygen level changes?
    Keep up the helpful monitoring.

    • Jeremy Biggs Says:

      Hi John – thanks for the message. Yes – I will make test holes some time and I think I should probably do it in a pond where oxygen is going down.

      One of our neighbours has a more leafy pond where I could do this – I simply haven’t managed to find the time to do that yet.


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