How to build a wildlife pond

A wildlife pond is a pond without fish. That single choice does more for frogs, newts and insects than any gadget. The RHS says fish are top predators in a garden pond, they raise nutrients, and they encourage algae. If the pond you inherited is full of goldfish, rehome the fish or dig a second pond. Do not tip them into a local river or lake.

Shape and depth

Follow the RHS wildlife pond guide:

• At least one side is a long, shallow slope, so animals can walk in and out, and so a drop in water level leaves a damp edge rather than a cliff.
• A varied depth of about 20–60 cm suits most of the plants and animals they have in mind. The construction page still wants ponds to be at least 38 cm somewhere, because very shallow water overheats and freezes. A beach plus a deeper pocket covers both.
• Even a pot counts. If the pot is not sunk in the ground, add a ramp outside and inside.
• Butyl is the RHS's easy liner for a natural shape. A preformed shell usually needs a ramp because it has no beach. Liner sizing is on the liner page.

Put part of the pond in the sun and part in shade. Sun warms the water for spawning amphibians in spring. Shade slows algae. The construction guide says at least half the surface in full sun, and the ground reasonably level.

Autumn and winter are the RHS's preferred time to dig, after the breeding season and before amphibians settle into the mud. Fill with rainwater. Tap water is a last resort: it carries nutrients that feed algae. While the pond is filling, topping up explains why you should not rush to keep it brim-full in a dry spell. Seasonal ponds that drop in summer can favour newts, because the fish that would eat their larvae cannot live there.

Do not stock it from another pond

The RHS says wildlife finds a new pond quickly, and that moving frogspawn, mud or water from another pond can bring disease and invasive plants. Let it colonise. Planting, if you add any, is on the plants page.

Pumps and filters

The RHS filter page says a pond with few or no fish should not need a filter. You can keep a pump for a trickle if you want the sound, but it needs a guard so tadpoles are not sucked in. A UV clarifier is for green water in a system that already circulates. It is not a standard fitting for a wildlife pond.

Children still come first

A wildlife pond is not a safe pond. RoSPA's advice is the same whether or not you keep fish: restrict access while young children live in the house or visit. A beach that helps a frog can also tempt a toddler. Read pond safety before you fill the hole. The RHS says the same thing in its construction guide: if young children can reach the garden, keep the pond out of reach unless they are supervised, and consider a fence or a metal grid. On grids, follow RoSPA rather than a grid placed under the water. The safety page explains why.

The edge of the garden

Let grass grow long on one side so young frogs have cover. Stop the turf short of the water. The RHS warns that grass roots wick water out of the pond surprisingly fast. A gravel or mud beach is a drinking spot for birds and hedgehogs as well as a way out for amphibians. Plankley is the sister site for the hard edging if you want a paved side. Keep a robot mower's boundary back from the beach. Gladeburn covers those mowers.

Can I add a few goldfish later?

The RHS advice is not to, if the point of the pond is wildlife. Goldfish change the pond. Build a separate fish pond if you want fish.

When should I dig?

The RHS says autumn and winter disturb breeding wildlife least, and rain is more likely to be available for filling. If children are in the garden, do not leave a half-filled hole unfenced while you wait for rain.