Do leaves use up oxygen in garden ponds?

I like leaves in my pond

Many guides tell people to remove leaves from their ponds. Here’s a typical piece of advice:

‘When leaves fall in the autumn, try to keep them out of the pool if you can and rake out those that do get in.’

And a typical reason for doing it:

If vegetation falls into the pond water and decays the process of decay uses the oxygen in the water and releases carbon dioxide. This means that if large quantities of vegetation enter your pond then enough oxygen can be removed to cause the pond’s wildlife to suffocate.

Is any of this right?

I can only go from my own experience. In our garden the pond is now going through its second autumn: as you can see, there are quite a lot of trees and shrubs nearby, and they drop leaves into the pond.

Despite this, there is no shortage of oxygen in the pond. Todays there’s just over 11 milligrammes of oxygen dissolved in every litre of water in the pond – which is almost as much as it is physically possible to get in water at todays temperature (the techy term is that the water is 90% saturated).

This is enough for salmon or trout, the most oxygen demanding of fish.

So shortage of oxygen is not a problem at the moment. The leaves seem to be haivng little effect on the dissolved oxygen at present.

What will happen as the pond ages and more leaves fall? That will be interesting to find out. Will the pond get ‘worse’. Will it become a poorer wildlife habitat? I suspect not – but we’ll need to wait to find out.

Tags: Oxygen in ponds