The Garden Pond Blog

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.

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