Pond oxygen levels over Christmas

My two ponds have been frozen now for nearly two weeks.

With the rain of the last couple of days the ice is beginning to melt at the edges, but when I made the latest measurements yesterday evening ice still covered most of both ponds.

Oxygen in the old pond is still well above normal levels still, mirroring the pattern of last year. It should go down as the ice melts.

The oxygen level in the new pond is also interesting: it has stayed pretty constant throughout the freeze. Probably there are not enough plants in the water to raise it very much.

Quite why levels rose in this pond yesterday I don’t know: one possibility is that with the day’s heavy rain, and the slight melting around the edges, better oxygenated water entered the pond. But that’s just an educated guess.

The one thing that hasn’t happened in these two ponds is that oxygen has gone down during the icy weather.

Of course, these ponds are a little different to most others: shallower, clearer and with more plants.

The next thing to explore is what happens in more typical garden ponds when they ice over. Our measurements show these often have quite low oxygen levels.

How these ponds respond to icing over will be something to test in the next cold spell.


2 Responses to “Pond oxygen levels over Christmas”

  1. Joy Smith Says:

    We have a fibreglass lining which seems to have cracked and most of the water has disappeared – leaving our poor goldfish in minimal water which seems to have frozen completely. Will the fish survive? I fear not.

    • Jeremy Biggs Says:

      Dear Joy

      I agree: if the water is frozen solid and there’s very little liquid water underneath, they probably won’t make it.

      Can you rescue them into something deeper? We use those bendy plastic tubs you can get in garden centres. You can fill these with tap water and, before they freeze over, add the fish. The important thing is to make sure that the temperature of the water you move them to is the same as the pond.



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