Garden ponds

A pond brings more life into a garden than any other single feature, and it does not need to be large: a square metre of water attracts frogs, dragonflies and bathing birds. The decisions that matter most are made before any digging starts.

Children and safety

A small child can drown in a few centimetres of water, silently and within moments. The Royal Society for the Prevention of Accidents (RoSPA) reports that garden ponds are involved in about a quarter of child drownings in the home. Its advice for households with young children, or visited by them, is:

• to fill the pond in until the children are older, turning it into a flower bed or sandpit, which it describes as the best option;
• otherwise, to cover it with a rigid metal grille strong enough to bear a child's weight, checked regularly; chicken wire is not adequate;
• or to fence it to a height of at least 1.1 metres with a locked gate, bearing in mind that young children climb well;
• to supervise closely near any pond, including those in the gardens of relatives and neighbours.

Where to put it

A pond does best where it receives sun for at least part of the day, on level ground, and away from overhanging trees, whose leaves foul the water in autumn. A position visible from the house adds to the pleasure of it. The lowest point of the garden is not always suitable, since ground that floods can lift a liner.

Shape and depth

Most pond life lives in shallow water. A wildlife pond needs broad, gently sloping margins, with much of its area less than 30 cm deep, and at least one side shelving gradually to the bank so that frogs, hedgehogs and birds can get in and out. A deeper section of about 60 cm stays cool in summer and unfrozen in winter. Ponds for ornamental fish need to be larger and deeper.

Liners

• Flexible liners of butyl or EPDM rubber fit any shape and last for decades. The hole is cleared of stones and lined with sand or a fleece underlay first.
• Preformed ponds of rigid plastic or fibreglass are quick to install but often have steep sides, which can be softened with a ramp of stones.
• Containers such as half-barrels, old sinks and troughs make miniature ponds for patios and small gardens.

Filling and planting

Rainwater is best for filling and topping up. Tap water contains nutrients that feed algae, and a pond filled with it often turns green for a time before settling.

Plants keep the water clear by shading it and by using up nutrients. A balanced planting has three kinds:

• Submerged plants, such as hornwort and spiked water-milfoil, which oxygenate the water;
• Floating-leaved plants, such as water lilies and frogbit, which shade the surface;
• Marginal plants, such as marsh marigold, water forget-me-not and brooklime, which grow in the shallows and give cover to emerging insects and young frogs.

Aquatic plants are planted in baskets of low-nutrient aquatic soil or directly into a layer of washed sand and gravel, never in garden compost.

Several aquatic plants once sold for ponds have become serious pests of rivers and lakes. The sale of water fern, parrot's feather, floating pennywort, New Zealand pigmyweed and water primrose has been banned in England and Wales since 2014. No pond plant, native or otherwise, should be discarded in the wild.

Fish or wildlife

Fish eat tadpoles, newt larvae and most aquatic insects, and their waste enriches the water. A pond intended for wildlife is better without them. Goldfish and koi need larger volumes, a pump and usually a filter.

Frogs, newts, water beetles and dragonflies find new ponds unaided. Moving frogspawn or plants from another pond risks carrying disease and invasive species with it, and conservation bodies advise against it.

Looking after a pond

• Autumn: a net stretched over the surface catches falling leaves. Overgrown plants are thinned in late autumn, when least wildlife is disturbed, and the removed material is left on the bank for a day so that animals can return to the water.
• Winter: a sheet of ice does little harm to a wildlife pond. Breaking it by force can injure animals beneath.
• Spring and summer: blanket weed is wound out on a stick. Barley straw, placed in a mesh bag in spring, slows the growth of algae as it rots. Water lost to evaporation is replaced from a water butt.

Green water in a new pond usually clears without treatment once plants are established.

Pumps and electricity

A wildlife pond needs no pump. Fountains and filters can be run from low-voltage or solar-powered pumps. Any mains electricity outdoors is protected by a residual current device, and in the United Kingdom a new outdoor circuit is installed by a registered electrician.

More on ponds and other habitats is given under gardening for wildlife.