A pond needn't be a big-garden project. A half barrel, an old butler's sink or a rigid liner sunk into a border will support frogs, newts, dragonflies and a whole cast of invertebrates — and it will do it within a couple of metres of your kitchen window. Get four things right and the rest looks after itself: siting, depth, planting, and access. That last one is the detail most people miss, and it's the difference between a pond that welcomes wildlife and one that traps it.

Choosing a container and the right spot

Aim for a container at least 60cm across and 45cm deep. Frogs and newts need enough depth to overwinter below the ice; a shallow dish will freeze solid and kill them. A half barrel — typically around 70cm wide and 40–45cm deep — is ideal, and a well-made one will outlast most plastic. Rigid preformed liners in a tub or trough shape work just as well, and if you sink one flush with the ground it looks more natural and lets wildlife walk straight in.

For position, think half sun and half shade. A few hours of sun warms the water for tadpoles and encourages plants to flower, but full sun brings blanketweed and constant evaporation. Avoid overhanging trees, which drop leaves and draw up moisture, and avoid deep shade, where little grows and few insects visit. Set the pond near a shrub, a patch of long grass or a log pile so frogs have cover on the journey in.

Two practical points before you fill it. Check the base is level in both directions with a spirit level — a barrel on bare soil will settle unevenly and tip. Raise barrels on a firm footing of paving slabs or compacted gravel. And never introduce fish: even a couple of goldfish will clear a small pond of tadpoles, larvae and newts within a season.

Making it safe to enter and leave

This is the part that matters most. Hedgehogs drown in steep-sided ponds, and so do frogs that can't find a way out. Build a shallow beach at one end — a wedge of gravel and pebbles sloping from the water surface up to the rim. Alternatively, stack a few flat stones to make submerged steps, or lay a piece of weathered wood or a couple of bricks at an angle so they break the surface.

Leave the water level 5–10cm below the rim. That small gap gives anything that arrives over the edge a fighting chance of crawling back out, and it stops the pond overflowing in a downpour. If you have small children, a raised barrel with a stout mesh cover is the safest option — or wait a few years.

Planting with native oxygenators

Plant in spring or early autumn. Submerged oxygenators are the engine of the pond: hornwort, water starwort and spiked water milfoil are all British natives that release oxygen, mop up nutrients and give tadpoles somewhere to hide. Buy a couple of bunches, weight them or tuck them into a small basket of aquatic compost topped with gravel, and drop them in.

Around the edges, marsh marigold gives you early yellow flowers when little else is out, and water forget-me-not thrives in the shallows where frogs like to sit. Lesser spearwort is another good native for a small space. If your barrel catches the sun, add a dwarf water lily in a basket, or float a little frogbit on the surface for shade and cover.

Steer clear of floating pennywort, water fern and parrot's feather. These non-native invasives are banned from sale in the UK for good reason — they'll smother a small pond in a single season and are almost impossible to remove.

Filling, and the first few weeks

Fill with rainwater from a butt wherever possible. Tap water carries the nutrients that feed algae, so if you must use it, let it stand for a few days first. Then leave the pond alone for a fortnight. It will look alarmingly green, and then it will clear as the plants and microscopic life settle into balance. A green flush in the first spring is normal and temporary.

Life arrives fast. Water beetles, pond skaters and water boatmen appear within days, followed by damselflies and dragonflies laying eggs. Frogs and newts usually find a new pond within a season or two, especially if there's another pond nearby. Resist the urge to add frogspawn — let them come. Birds will drink and bathe at the edge, and bats will skim the surface at dusk.

Caring for it through the year

Keep maintenance gentle — a wildlife pond is meant to look a little untidy.

• Autumn: net out fallen leaves, but leave a few in. They shelter invertebrates and break down slowly.
• Spring: thin oxygenators if they've filled the space, and twirl excess blanketweed out with a stick, leaving some for tadpoles to graze on.
• Winter: float a ball or a small piece of timber so ice can expand safely and gases escape. Never smash the ice — the shock can kill frogs resting below.
• Summer: top up with rainwater during dry spells, and keep slug pellets, weedkiller and fertiliser well away from the pond edge.

Never empty and scrub the pond clean. The silt at the bottom is where larvae, newts and frogs spend the winter, and it's the whole point of the exercise.

Start small, get the slope right, plant natives and then mostly leave it be. Within a year you'll have a corner that hums, croaks and glitters — in a space no bigger than a water butt.