Is removing half the water in the pond, followed by a rainwater top-up, likely to be good for wildlife?

Joe asked in the comments what I thought about half-changing the water in a pond – something that’s pretty widely recommended.

Well….removing half the water and topping up with rain water should reduce pollutant levels, but whether it reduces them enough to make a difference might be another matter.

Nutrients, in particular, need to get down to a pretty low level to be ‘safe’ for wildlife: if the half dilution didn’t get down to that level the benefits might not be as much as you’d hope.

As so often, at the moment the problem is that no-one has carefully observed the effects on wildlife in ponds where this kind of water change has been done, so it’s hard to give anything other than a tentative answer.

And because a lot of nutrients can be locked up in sediments and plants (a re-released into the pond) there’s a good chance you’d need to combine water changing with regularly removing plant material and sediments to have a chance of success.

But to be honest, at the moment we’re all a bit in the dark about how effective a technique this would be.

But before yuo get to gloomy remember that, even if the pond does have some management problems it’s still going to have a lot of life in it – it’s just that it may not reach it’s full potential.

If you’re worried, one thing we can do is have a look at the pond conductivity – send us a sample and we can check whether watr changes might be a good idea or not.


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