Now I solve marital disputes too

A fence

Richard asks:

“Perhaps you could settle an argument between my wife & I – our pond is quite small (less than 1 square metre) – should we clear out leaves? My wife says yes to stop algae building up and I say no because it’s a habitat for small pond critters.

Who, if anyone is right?”

Well, the picture above is a clue to my answer.

Leaves and debris are indeed habitat: in my pond the place I see most Broad-bodied Chaser dragonfly larvae is the leafy overhung bit. But my pond is quite a bit bigger than Richard’s so maybe it’s unsual.

At the other extreme is this pond.

Overwelmed by leaves

This one is probably a bit overwelmed by leaves.

But do you need to remove leaves to stop algae building up? Well the truth is no-one really knows.

Leaves might cause the growth of algae by adding nutrients to the water – which is why removing them might be something you need to do.

But although plenty of reputable people suggest this is necessary, the amount of fertiliser in the leaf as it fallls off the tree is quite small (trees take them out of the leaves before dying – no fools trees). I did some rough, back of the envelope, calculations here on the quantity of nutrients in dead leaves.

My conclusion is that you need a lot of leaves to add a signficant amount of nutrients to the pond.

So probably the truth is somewhere in between. I make no effort to stop leaves getting into my pond but if you’ve got a lot falling in, then you might do.

Until there is a better answer – which needs some careful observations of garden pond sized ponds with different quantities of leaves in them – the best guide is the animals.

If there are animals living amongst the leaves, and the rest of the pond has a reasonable variety of animals too, then things are probably OK.

And don’t forget the algae might be there because of polluted water – nothing to do with the leaves.

And another thing: leaves may themselves stop the growth of algae by releasing tannins into the water.

My answer creates domestic harmony

My answer creates domestic harmony


2 Responses to “Now I solve marital disputes too”

  1. Richard Says:

    Thank you for sorting out our matrimonal dispute, the leaves from the Hibiscus are now floating (and sinking) in the pond.

    If you’re still after ponds to survey in Abingdon, then ours is open for inspection – it’s small and new.

  2. pondolive Says:

    On the whole I think leaves do not stimulate algal growth – they contribute very little nutrient and the bacteria breaking them down probably lock up nutrients in the sediments. Plus tannins tend to inhibit algal growth. Leaves are indeed habitat and food source and many invertebrates depend on decaying leaves as a food source.

    But… decaying leaves can have a big impact on submerged plant growth and on dissolved oxygen. They decay into a gloopy black sediment that can’t support much plant or animal life (black colour in soils is nearly always an indicator of low oxygen levels). This is why most people advise you to limit the number of leaves falling into a pond. All ponds can cope with a certain amount of leaf fall into them and this is perfectly natural, but if you want to maintain a high quality pond – and especially if it’s small – I recommend clearing out any accumulation of leaves every second or third autumn. If your pond fills up with leaves every year, it’s in the wrong place and you should consider either building another pond elsewhere or taking some loppers to the offending vegetation.


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