Garden ponds provide fantastic wildlife habitats, but they can attract algae and duckweed, too.


A small amount of algae or pondweed is beneficial to ponds, providing food for tadpoles and other water creatures, but too much can block light from submerged plants and prevent them from photosynthesising, reducing oxygen levels in your pond.

How to remove duckweed and blanketweed from ponds

Ponds almost inevitably develop a covering of green duckweed or blanketweed over summer. In this Gardeners' World programme clip, Monty Don highlights the various ways to control these fast-growing pond invaders, and what to do with the vegetation after you remove it:

More on garden ponds:

Find more tips on keeping your pond water healthy and clear, below.

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You will need:

  • Oxygenating plants
  • Barley straw
  • Pond conditioner

Step 1:

Oxygenate the pond using oxygenating plants. Plants such as hornwort and elodea, which sit below the surface, will add oxygen to improve water quality.

Adding oxygenating plants to a garden pond

Step 2:

Add barley straw. Barley straw limits algal growth by absorbing excess nitrogen. Remove straw after six months, or when it has turned black.

Adding barley straw to a pond

Step 3:

Condition the water. If you top up your pond with tap water, add a conditioner (available from garden centres or online) to remove chlorine and minimise algae.

Adding water conditioner to a pond