Keeping pond water clear

Tim Rumball looks at how to control blanket weed and algae bloom

- Tim Rumball

A GARDEN pond is great fun, offering an opportunity to grow different plants and enjoy aquatic wildlife or ornamental fish. When well stocked with the right balance of oxygenating and shade plants, pond water should be clear. However, if the balance goes wrong, algae (microscopic plants) thrive and take over.

There are two common types of algae. Green water algae turn the pond water into an opaque green soup, while string algae, known as blanket weed, produce billowing clumps in fine strands. Both are unsightly and can be harmful to plants and wildlife as they reduce oxygen levels in the water.

Contributing factors to their appearance include high nutrient levels in the water, rising temperatures and too much sunlight penetrating the surface. Shallow ponds less than 2ft (60cm) deep are more prone to algae blooms.

Clear the way

First, clear heavy infestations of string algae. All ponds have some algae, but it’s the rampant growth that must be kept in check. String algae or blanket weed can be twirled onto a stick or a rake thrust into the water, then pulled out.