Where to place a preformed pond? Location, size and site preparation

This guide helps you choose where to place your preformed pond (sun, trees, slope, electricity, view), which shell size to choose, and how to prepare the ground. For the construction itself—excavating, bedding on sand, backfilling, and filling—follow the Step-by-Step Shell Installation section further down in this guide.

How to place a preformed pond shell? Discover our complete guide. Water brings a magnetic appeal to any garden; it is an essential visual feature. Are you thinking of placing a preformed pond in your garden?

Preformed shells simplify pond construction and are perfectly suited to gardeners who are still relatively inexperienced. These preformed shells are available in different sizes and shapes. Find all our preformed ponds here.

Here is a guide created by our partner: Oase Living Water

Step 1: Workload

Allow 1 to 2 days for installing the preformed shell and technical elements. The filtration system must be suited to what you want to do with the pond. Fish? Plants? Visit our filtration kit section or send us a message at support@foudebassin.com. We recommend not choosing a filtration system that is "barely adequate" so that you do not have to clean your filtration system too often.

Tools and materials required

For building the pond, you will need existing gardening tools such as a shovel, spade, wheelbarrow, and marking spray. Also, remember that a spirit level and a carpenter's level or tape measure will be necessary.

Where to place the shell: the criteria that matter

A shell cannot be moved once backfilled. Take the time to compare two or three locations before taking the first shovel of dirt. Here is what we check with our customers.

• The sun: 4 to 6 hours of direct sunlight, ideally with shade during the hottest hours. A small volume of water heats up quickly in full sun.
• Trees: place the shell out from under the drip line of the foliage. Leaves that fall into the water in autumn decompose at the bottom and load the pond with organic matter; roots, on the other hand, can grow against the shell.
• The terrain: choose flat ground and avoid the lowest point in the garden, where rainwater runs off and brings soil and fertilizer into the pond.
• Electricity: the pump and filter need power. The closer the pond is to the house, the shorter the trench and conduit will be.
• The subsoil: locate buried cables, pipes, and drains before digging.
• The view: the pond should be visible from the patio or a window. That is where you will enjoy it the most.

What shell size to choose?

The volume is chosen according to what you want to accommodate, not just according to the available space. The larger the volume, the more stable the water remains in temperature and oxygen.

• Plant pond or decorative water feature: all sizes are suitable. A shell with steps makes it easier to plant bank plants.
• Goldfish: they live very well outdoors, provided they have a deep area of 80 cm to 1 m to spend the winter. Most shells are shallower: choose the deepest one possible.
• Koi carp: we recommend at least 5 m³. This is beyond most shells; an EPDM liner will then be more suitable.

Buried or above ground?

A shell to be buried blends into the garden and keeps the water cooler in summer. Models designed for above-ground installation, often made of polyester, are placed on flat and stable ground: practical on a patio, on ground that is difficult to dig, or to keep the water at eye level. Always check on the model's product page that it is intended for this use.

Preparing the ground before installation

Once the location is chosen, a few preparations will prevent unpleasant surprises on the day of the construction:

• Trace the outline of the shell on the ground and observe it from the house.
• Plan where to store the excavated soil, which represents more than the volume of the shell.
• Check access for the wheelbarrow and removal of debris.
• Order the sand for the bedding and the side backfill.
• Plan the passage of the electrical conduit and have the connection done by an electrician.
• Choose the filtration system at the same time as the shell, according to the volume and planned fish.

Everything ready? Move on to the installation, detailed just below, to install a preformed pond step by step.

Installing the shell step by step: excavating, bedding, backfilling, filling

A properly installed shell does not rest on a few hard points: it is supported everywhere by sand. This is what prevents it from deforming or cracking under the weight of the water. Allow sand for the bedding and backfill, soil or gravel for the surroundings, an electrical conduit and a warning mesh, as well as the pump and filter.

1. Trace the outline: place the shell upside down on the ground and mark its outline with a paint spray or a garden hose, adding a margin of about 5 cm all around.
2. Excavate: first remove the grass, then dig following the shape of the steps, without going too deep. Measure the depth with a tape measure and remove all stones, which could damage the shell.
3. Make the sand bed: spread a layer of sand at the bottom of the hole and level it.
4. Place the shell: push it into the sand, then check the level with a straight board placed across and a spirit level, lengthwise then widthwise.
5. Fill to one-third: add about ⅓ water and let it rest for 2 to 3 days, long enough for the weight of the water to compact the sand.
6. Fill the sides: pour sand into the empty space, water it, push it under the steps with a stick, and raise the water level at the same pace, until completely filled. Recheck the level after each pass.

At the same time, dig a trench to your electrical network to bury the power supply in a conduit, between 60 and 85 cm deep, with a warning mesh about 20 cm above. The connection to the panel and the protection of the circuit is the job of an electrician.

Connecting the pump and filter, then finishing the edges

Place the pump at the bottom of the shell, on a stable surface, and the filter outside, near the edge, in an easily accessible place for maintenance. If the filter works by gravity, it must be placed higher than the pond so that the filtered water returns to it. Run the pipes over the edge of the shell: do not drill a shell that is not designed for this. Our complete filtration kits combine a pump and a filter sized according to the volume of the pond.

The plastic edge of the shell is the least attractive part of the pond. To make it disappear:

• flat stones placed slightly overhanging the water, on a stable bed, without weighing directly on the edge of the shell;
• stepping stones or pebbles;
• bank plants and aquatic plants placed on the steps, which hang over the edge.

More ideas in our article for hiding the edges of a preformed pond.

Frequently Asked Questions

Can you place a preformed pond in full sun?

It is not ideal. We recommend about 4 to 6 hours of direct sun, with shade during the hottest hours. A small volume of water in full sun heats up quickly and promotes water imbalance.

Can you install a shell under a tree?

It is better to avoid it. The leaves that fall into the water decompose at the bottom of the pond, and the roots can grow against the shell. Place it out from under the drip line of the foliage.

What size preformed pond for goldfish?

The main criterion is depth: an area of 80 cm to 1 m allows them to spend the winter outdoors. Choose the deepest shell possible and the largest that your location allows.

Can a preformed pond remain above ground?

Yes, if the model is designed for this, which is the case for several polyester shells. It is then placed on flat and stable ground. A shell designed to be buried should not remain above ground.

Should you fill the shell before or after backfilling?

Both at the same time. Start with about one-third water and let the soil settle for 2 to 3 days. Then, fill the sides with watered sand while the water level rises, until completely filled.

Why does my shell deform once filled?

Almost always because the sides are not supported: insufficient backfill, poorly compacted, or voids under the steps. The pressure of the water then pushes the walls outward.