How do you make a wildlife pond?
By building something that suits the animals rather than the gardener — and the two decisions that matter most are shallow sloping edges and no fish, both of which are frequently got wrong.
Why ponds matter so much. Adding water is widely regarded as the single most effective thing a garden can do for wildlife. A large proportion of ponds in the wider countryside have been lost, and garden ponds now support a meaningful share of some amphibian populations.
The essentials:
Shallow, gently sloping edges on at least one side — the single most important feature. Animals need to get in and out: amphibians, hedgehogs, birds bathing, and insects emerging. A pond with vertical sides is a trap, and drowned hedgehogs are a common consequence.
A range of depths. Shallow margins for most life, and a deeper area — around 60cm or more — that will not freeze solid or overheat.
No fish. This is the decision people resist most. Fish eat tadpoles, larvae and invertebrates, and a pond with fish supports a fraction of the diversity of one without. You can have a fish pond or a wildlife pond, and the compromise mostly favours the fish.
Sunlight on part of it, since most pond plants and insects need it, with some shade to limit algae.
Rainwater rather than tap water where possible, since tap water is high in nutrients that feed algae. Allow a butt to fill it, or let it fill naturally.
Native plants — submerged oxygenators, floating leaves to shade the surface, and marginal plants for cover and for emerging insects.
Cover around the edges — long grass, logs, stones — since amphibians spend most of the year out of water and need somewhere to be.
What not to do:
Do not introduce spawn or animals. They arrive on their own, usually within a season, and moving spawn spreads disease and invasive plants.
Do not use invasive aquatic plants, several of which are banned from sale for good reason.
Do not clear it out thoroughly. Some sediment and leaf litter is habitat, not mess.
Even a very small pond works — a sunken washing-up bowl with a ramp supports a surprising amount.