How do you build a garden pond? Depth, steps and costs

• Sun: 4–6 hours a day — more breeds algae, less starves the plants.
• Not under trees: falling leaves feed algae and roots threaten the liner.
• Three depth zones: marsh (0–20 cm), shallow (20–40 cm) and deep (80–100 cm) — a place for every plant, and frost-free wintering for fish and frogs.
• On clay: the firm base here is an advantage; mind the high water table though — groundwater can push an empty liner up.
• Safety: with toddlers choose a raised pond or a grid just under the surface.

1. Mark the shape with a garden hose and dig the depth zones in terraces.
2. Remove roots and stones; lay protective fleece.
3. Fit EPDM liner (30+ year lifespan) loosely with generous overlap.
4. Finish the edge with stone, timber or a marsh zone — the edge decides how natural it looks.
5. Fill with (rain)water, let it settle for a week, then plant the zones — oxygenators first.
6. Technology is optional: a well-planted natural pond needs no pump or filter; fish or a formal design do.

Best building season: spring (April–May), so the planting matures before summer.

• Oxygenators (underwater): hornwort, waterweed — 3–5 bunches per m² keep water clear.
• Floating leaf: water lily and frogbit shade the water and suppress algae; cover a third to half of the surface.
• Marsh and edge plants: marsh marigold, yellow iris, purple loosestrife — nutrient consumers plus an exit ramp for wildlife.

Green water in the first weeks is normal and clears once plants establish. Skim thread algae with a rake; fight the source (leaves, feed, too few plants), not the symptom.