← 🏠 Homeowners and DIYers toolkit
Pond Planner: Liner, Cost and Fish, Step by Step
Plan a new pond in the order you will build it, with the cost of each stage as you go.
Part of the 🏠 Homeowners and DIYers toolkit, with more tools made for the job.
Plan the size of your pond
Measure the hole you have dug or marked out, in metres. You need three measurements. This sets the liner, the water and the pump.
The longest distance across the top.
The widest distance across the top, at right angles to the length.
From the top edge down to the lowest part.
The extra liner left over the edge. Leave empty for 0.3 m. Suppliers suggest about 15 cm to 1 m.
Only for the water volume. Add the shallowest and deepest depths and halve it. Leave empty to use the deepest.
Fill in these measurements and the liner you need appears here.
Dig the hole and prepare the base
Before any liner goes in: digging, taking the soil away and making a smooth, stone-free base.
Fill in step 1 first. The items priced by area use the liner size from there.
Lay the liner
The liner itself, priced by area on the size from step 1, and anything you need to fix it.
Fill in step 1 first. The items priced by area use the liner size from there.
Edge the pond and finish the surround
Hiding the liner edge and making the area around the pond look finished.
Add the pump, filter and features
The equipment that keeps the water moving and clean, and anything you want to look at or listen to.
Which pump to look for
Leave empty for 1. Fish ponds often want 1 or more.
Fill in step 1 and the pump size appears here.
Mains electrics near water should be fitted by a qualified person. Check the rules where you live.
Fill it and plant it
Filling with water, making it safe for life, and the plants that keep it healthy.
Add the fish
Last, and gradually. The cost of the fish, and a check that the pond is big enough for them when they are grown.
Will they fit?
Not the size you buy them. Ask the seller for the adult weight.
Type how many fish and how heavy each will be when grown, and a check appears here.
These are rules of thumb from pond suppliers and hobby guides, and they differ by a factor of two. Ask a specialist about your fish and filter.
Running it each year
Once it is built, a pond still costs something. This is not part of the build cost above.
On the pump label.
Leave empty for 24. Most pond pumps run all day.
Filter media, water treatment, replacing plants.
Your pond, step by step
What each part of the build adds, and the total.
Type some prices in steps 2 to 7 and the whole cost appears here, step by step.
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Start with the size of the pond. This gives the liner to buy, the water it holds and the pump to look for. Then work down the page through each stage of the build, typing what each part costs, and see the total grow.
Building a pond is a series of jobs in a fixed order: dig the hole, lay the liner, edge it, fit the pump and filter, fill it and plant it, then add the fish. Each has its own costs, and the liner is often a small part of the bill. Going through them in order helps you picture the build and stops the costs you forget, like removing the soil, the underlay, a pump big enough for the water, and a year of running it. The liner is the pond's length plus twice the depth plus twice the overlap, each way. Once you know the water volume, you can size the pump, and check that the fish you want will not be crowded when they are fully grown.
How it’s worked out
- Step 1, the size: the liner is the length plus twice the depth plus twice the overlap, and the same for the width. It is rounded up to the next half metre or foot, and the water volume is the surface area times the average depth.
- Steps 2 to 4, the groundwork: digging and removing the soil, the underlay and liner (priced per square metre or foot on the rounded liner size), and the edging and surround.
- Step 5, the equipment: the pump, filter, pipes, any waterfall or fountain and the electrics. The pump to look for is the water volume times how often an hour you want it passed through, with a margin of 1.5 to 2 times for lift and pipework.
- Steps 6 and 7, the life: water treatment, plants and fish. The stocking check divides the fully grown weight of your fish by the water in thousands of litres and compares it with the range guides give.
- Step 8, running it: the pump's power times the hours it runs times the electricity price, plus fish food and the odds and ends, per year.
- The summary adds each stage with a running total, plus a share for surprises. If you leave it empty, 10 percent is used.
A 3 m by 2 m pond 0.6 m deep with 0.3 m overlap needs a liner of 4.8 m by 3.8 m, so ask for 5 m by 4 m, and with an average depth of 0.4 m it holds about 2,400 litres. Passing it through the pump once an hour is 2,400 litres an hour, so look at pumps rated nearer 3,600 to 4,800.
Common mistakes
- Measuring the surface and forgetting the depth. The liner goes down the sides and across the bottom, so depth counts twice.
- Budgeting for the liner only. The pump, filter, edging, plants, fish, water treatment and getting rid of the soil are usually most of the cost.
- Buying fish for the size they are in the shop. Plan for their fully grown weight, because a crowded pond needs more filtering and goes wrong faster.
- Making the pond too shallow for fish. Guides suggest around 90 centimetres (3 feet) for a pond that holds koi or goldfish.
- Choosing a pump by its box label. Flow falls with lift and pipe length, so check the maker's chart at your height.
- Forgetting the running costs. A pump that runs all day uses real electricity, and fish need feeding.
Questions
In what order do I build a pond?
Mark out the shape and dig the hole, make a smooth base with sand and underlay, lay the liner, edge it, fit the pump and filter, fill it with water and let it settle, add plants, and only then add fish, gradually. The steps on this page follow that order.
How much overlap should I allow?
Suppliers give different figures, roughly 15 centimetres to 1 metre on each side. More is safer for deeper ponds and for fixing under edging stones. Leave it empty for 0.3 m (1 ft).
What does a garden pond cost?
It varies hugely by size, materials and what you add. Guides treat the liner, pump and filter as the essentials, with plants, fish, edging, waterfalls and lighting on top. Type your own prices, since any fixed figure would go out of date or be wrong for your area.
How big a pump do I need?
A common rule is to pass the whole pond through the pump about once an hour, and more for heavily stocked fish ponds. Choose a pump rated roughly 1.5 to 2 times that figure to allow for lift and pipes, and check the maker's head-versus-flow chart. Waterfalls and fountains need extra flow.
How many fish can I keep?
Guides vary by about a factor of two. They suggest roughly 1 to 3 kilograms of fully grown fish per 1,000 litres, with koi at the lower end and a conservative level being safer. Your filter, planting and climate matter too, so ask a specialist, and add fish gradually.
Does the volume include the shelves and plants?
No. It is the water in a simple shape, so the real volume is usually lower. Treat it as a maximum, and be a little cautious with pumps and fish.
Where the method comes from
Estimates only
These are estimates and general information, not building, safety, legal or professional advice. Materials, coverage, waste and rules vary by product, project and place, so check the maker's instructions and your local rules, and use a qualified person for gas, electrical and structural work.
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