A pond the size of a bucket still counts

Ask any wildlife gardener what single change brought the most life into their plot and most will say water. The trouble is that a full-scale pond is a serious commitment of space, money and digging. The good news is that a container pond — a half barrel, a stone trough, a large glazed pot, even an old butler sink — packs a remarkable amount of habitat into something you can set up in a single afternoon.

Frogs, newts, damselflies, water boatmen and pond skaters all use small water happily. Birds will drop in to drink and bathe, and hedgehogs, bees and butterflies will come to the edge to sip. You are not making a pale imitation of a "proper" pond. In a courtyard, balcony or tiny back garden, a well-planted barrel is the proper pond.

Choosing and siting your container

Aim for something around 40 to 60 litres, roughly 45cm across and at least 30cm deep. A wooden half barrel with a butyl or plastic liner is ideal, as is a sturdy preformed tub. Avoid narrow-necked containers, shiny glazed pots that crack in frost, and anything so shallow it turns into a birdbath in July. Depth matters: it keeps the water cooler, gives amphibians somewhere to retreat, and reduces the chance of it freezing solid.

Siting is the bit most people get wrong. Choose a spot that gets a few hours of sun and some shade for the rest of the day. Full sun all afternoon will overheat a small volume of water and feed blanket weed; deep shade will leave your plants sulking and your flowering marginals refusing to bloom.

• Keep it away from overhanging trees, which shower it with leaves and suck the moisture from the soil.
• Put it on level, firm ground so it cannot tip.
• If you can, sink it a third of the way into a border. It looks more natural, insulates the water, and lets frogs and beetles climb in without a struggle.

Filling and planting

Fill with rainwater from a butt or water butt overflow. Tap water is full of nutrients and minerals that trigger algae blooms, and it takes weeks to settle down. If you must use it, let it stand for a few days first — but rainwater really is worth waiting for.

Add a thin layer of nutrient-poor aquatic compost or ordinary garden soil, no more than 3cm, and weight it down with a layer of gravel to stop it clouding. Then plant in baskets, raising them on bricks or upturned pots so each sits at its correct depth.

Your submerged plants are the engine of the pond. Native oxygenators such as hornwort, water starwort and water milfoil breathe life into the water, shelter tadpoles and compete with algae for nutrients. Around the edges, choose British natives: marsh marigold, brooklime, water mint, lesser spearwort, creeping jenny and ragged robin all work beautifully in a barrel.

A word of warning: never take plants from the wild, and never buy floating pennywort, New Zealand pygmyweed, water fern or parrot's feather. These are invasive and illegal to plant out in the UK.

Build in a gentle slope

This is the single most important design detail, and it is easy to overlook. A steep-sided barrel is a death trap for hedgehogs, which swim well but cannot climb out, and it exhausts frogs and fledgling birds.

Create an escape route in one of three ways:

• Stack flat stones or pebbles inside one corner to form a ramp to the rim.
• Lay a piece of rough timber or a strip of corrugated plastic from the water to the ground outside.
• Use a shallow basket of gravel to make a shelved "beach" just below the surface that small creatures can scramble up.

Check it stays in place after storms, and remember that a ramp helps wildlife in and out — it does not stop frogs arriving.

Keeping it healthy through the year

Resist the urge to add fish. They eat tadpoles, larvae and everything else you are trying to attract, and they foul small volumes of water quickly. You also need no pump and no filter; plants and rainwater do the work.

• Summer: top up with rainwater, and skim off excess duckweed with a net, leaving some for cover.
• Autumn: net out fallen leaves, but leave dying stems standing for overwintering insects.
• Frozen spells: float a small ball or a piece of wood to let gases escape, and wrap the barrel in bubble wrap if it sits above ground.
• Late spring: this is the right moment to tidy, thin crowded plants and clear silt — never in autumn or winter, when amphibians are hibernating in the mud.

Patience, and what will turn up

The first year often looks quiet. Then, on a mild evening in February or March, frogspawn appears as if from nowhere. Damselflies arrive in June, hovering before they settle on a stem. Pond skaters colonise within weeks.

Do not move spawn or tadpoles in from another pond; you risk spreading disease and disturbing protected species. Let your barrel be found. If you have small children, keep the container behind a low barrier and supervise, and always check the water before emptying a pot or moving anything in spring. Give it a full year before you judge it — by then you will wonder how the garden ever managed without.