How to Build a Pond: A Step-by-Step Guide

Building a backyard pond is one of the most rewarding projects you can take on. It's hard work, mostly digging, but it doesn't need special skills or expensive tools. Plan it carefully, take each stage in order, and you'll end up with a pond that's easy to look after for years.

This guide takes you through the whole job, from choosing the spot to adding your first fish.

Step 1: Plan your pond

Choose the spot

Where you put the pond matters more than almost anything else. Look for a place that's:

• Sunny, but not all day. Around 4 to 6 hours of sun suits water lilies and most pond plants. Full sun all day encourages algae.
• Away from trees. Falling leaves rot in the water, and roots make digging hard and can damage the liner.
• Level and not in a dip. Rain running off the lawn carries soil, fertilizer and weed killer into the pond. A spot that's level or slightly raised stays cleaner.
• Close to power. The pump and filter need a GFCI-protected outdoor outlet. A pond near the house is easier to wire and easier to enjoy.
• Visible from the house. You'll spend more time enjoying a pond you can see from a window or the patio.

Choose the size

Bigger ponds are actually easier to look after. A larger volume of water changes temperature more slowly and dilutes waste better, so it stays clearer and healthier. If you're torn between two sizes, go for the larger one.

Decide what the pond is for, because that sets the depth:

Liner or kit?

Most ponds use a flexible rubber liner, which lets you dig any shape you like. A preformed shell is quicker for small ponds. If you'd rather buy everything in one go, a pond kit bundles the liner, pump and filter, matched to each other. Our pond liner guide compares the options.

Step 2: Mark out and dig

1. Lay out the shape with a garden hose or rope. Simple, flowing curves look natural and are much easier to line than tight bends. Live with it for a day or two and look at it from the house.
2. Mark the outline with spray paint or flour, then lift the turf. Save it to patch bare spots later.
3. Dig the whole area to shelf depth first, about 8 to 12 inches.
4. Mark a shelf about 12 inches wide around the edge, where marginal plants will sit. Leave it in place and dig the middle down to full depth.
5. Slope the sides slightly rather than cutting them straight down. Sloped sides are less likely to collapse, and they're easier to line.

Step 3: Level the edge

This is the step people most often rush, and it's the one you'll notice most. Water is always perfectly level, so if the rim isn't, liner will show on one side and water will spill over the other.

Lay a long, straight board across the hole with a spirit level on top, and check all the way around. Build up low spots with packed soil and cut down high ones until the whole rim is level. For a long pond, a water level (a clear hose filled with water) works well.

Step 4: Lay the underlayment and liner

1. Clear the hole of stones, roots and anything sharp. Spread an inch or two of sand on the floor if the soil is stony.
2. Lay underlayment over the whole hole. This thick fabric protects the liner from punctures.
3. Work out the liner size you need: pond length + (2 × deepest depth) + 2 ft for overlap, and the same for the width.
4. Lay the liner in the hole, ideally on a warm day when it's soft and easy to shape. Work in socks or bare feet, not shoes.

Our pond liner guide explains which material to choose and how to fold it neatly.

Step 5: Fit the pump, skimmer and filter

Set up the equipment before you fill the pond and finish the edges. That way you can still bury pipes and hide cables.

• Put the intake and the return at opposite ends. If the skimmer or pump is at one end and the filter or waterfall at the other, water circulates through the whole pond.
• Size the pump to turn over the pond's volume every 1 to 2 hours, or every hour for koi. Check its flow at your real head height. Our pond pump guide explains how.
• Fit the filter following the maker's instructions. If you want clear water, include a UV clarifier. Our pond filter guide compares the different types.
• Raise a submersible pump a few inches off the floor on a brick or flat stone, so it doesn't suck up sludge.
• Hide pipes and cables in a shallow trench, ready to cover with soil or stones later.

Step 6: Fill and finish the edges

1. Start filling slowly. As the water rises, pull the liner gently to smooth out folds, and gather the spare into a few large, neat pleats.
2. Fit the edging once the pond is about two-thirds full. Lay flat stones or pavers over the liner overlap, with a slight overhang to hide the liner.
3. Fill to the top, then let everything settle for a day or two before trimming the spare liner.
4. Switch on the pump and filter, and check every joint for leaks.

Step 7: Treat the water and add plants

Tap water usually contains chlorine or chloramine, which harms fish and the helpful bacteria in your filter. Add a pond dechlorinator that treats both, at the dose on the label for your pond's volume.

Then add plants:

• Marginal plants go on the shelves, in pond baskets, with their crowns at the depth on the label.
• Water lilies go in the deep zone. Start them on a raised brick and lower them as they grow.
• Submerged plants such as hornwort help keep the water clear.

Aim for plants to eventually cover around half the water's surface. They shade the water and use up the nutrients that algae feed on.

Step 8: Wait, then add fish

A new pond needs time before it's ready for fish. The filter's helpful bacteria take around 4 to 6 weeks to build up once the water is above about 50°F.

• Add a bacteria starter to speed things up.
• Test the water for ammonia and nitrite with a pond test kit. When both read zero, it's ready.
• Start with a few fish. Float their bag on the pond for 15 to 20 minutes so the temperatures even out, then let them swim out.
• Build up slowly over the following weeks, and don't overstock. Goldfish and koi grow much larger than they look in the store.

Ready to stock up? Our guides to fish ponds and koi ponds cover choosing fish and keeping them healthy, and our pond plants guide helps you choose what to grow.