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How to build a pond

In this tutorial we take a look at how to build a pond in your garden. Here are the guidelines for building the pond of your dreams!


The depth of the pond

I recommend that you make an excavation no deeper than 80 cm in the middle part.

This depth is perfect for both fish and aquatic plants, and also allows you to easily enter the pond to remove or place baskets of aquatic plants.

For large water lilies, 60-80 cm of water (including the basket) is a perfect depth!

If you want to add lotus flowers in addition to water lilies, you can add a shim under the baskets later. Lotus flowers prefer to be grown at a shallower depth than water lilies.

I also recommend that you create a step at a shallower depth around the perimeter of the pond in order to be able to grow marsh plants, which are not only aesthetically pleasing but also very important for the purification of the pond water.

In general, Marsh plants grow well at a depth of 5 to 15 cm from the water surface to the rhizome of the plant, so, considering that you have to plant them in a basket, this step should have 20 to 40 cm of water on it. If you use 15 or 18 cm high baskets (the most widely used for marsh plants), then you can simply create a step with 30 cm of water along the entire edge of the pond!

When calculating the depths of these tiers, you have to take into account the maximum water level of the pond (beyond which the water will overflow).

That is why I have prepared a diagram that will help you build your pond.

Come realizzare un laghetto

Exposure of the pond

I recommend that you place your pond in full sun, because aquatic flowers love the sun, so if you want to have abundant blooms, choose a sunny spot (either full sun all the day long or in an area where it gets sun for half a day, in the middle hours of the day or in the morning).

Avoid building your pond under a large plant because, in addition to poor flowering, you will often have to collect the dry leaves that fall in the water in autumn.

If so many dry leaves are deposited and not collected, they will rot at the bottom and during this process oxygen is consumed and nitrites are produced. In short, this process will produce algae in the spring!

To learn more about all these details and discover how to set up your pond with the appropriate aquatic plants, creating a perfectly balanced, algae-free pond in a natural way, download the free “Guide to Growing Aquatic Plants“.


Materials for building your pond

You can build a pond in 3 different ways depending on the available space and your type of ground.

You can build the pond by using a pre-formed plastic pond as a base, or by making an excavation of the size you want and using PVC liner to make it waterproof, or you can build a natural pond without liner if your ground is clayey and therefore already waterproof by nature.


How to build a pre-formed plastic pond

There are ready-made plastic pre-formed ponds on the market. All you have to do is make a small excavation, insert this structure into the excavation, and then you can put stones around the perimeter to cover the outer edges for aesthetic reasons.

This solution is very expensive and it is only suitable for small ponds, 1 to 3 square metres.

It is also an unversatile solution because you have to adapt to the shape of the structure, without being able to customise it. It is better, therefore, a pond with a liner.


How to build a natural pond with a clay bottom

A natural pond is a pond dug into the ground, of the shape and size you want, without the use of plastic structures or liners.

If the soil in your garden is clayey, you have the option of building a natural pond in which the clay itself acts as a waterproofing agent.

A clay soil is easily recognisable because it is a light brown soil tending to yellow or reddish. When it is wet it immediately becomes muddy and when it is dry it becomes hard as stone.

If you have such soil, you can excavate it and then compress the soil (e.g. with the bucket of an excavator), and then directly fill in the water!

Naturally, a pond with a clay bottom must be large and deep enough (80 cm) to retain water.

If you choose this method, you should also have the possibility of easily replenishing the water that (albeit very slowly) can be dispersed in the soil, e.g. via a nearby well or stream.


How to build a pond with PVC or epdm liner

If your soil is not impermeable, as in most cases, you should use PVC or epdm liner to build a pond in order to prevent water leakage. I recommend that you read this guide for choosing the appropriate pond liner.


Here are the steps for building a pond with a liner

  • Make the excavation in the shape and size you prefer;
  • Perfectly level the ground around the pond (if you have a lower side you will have to bring back some soil, or dig the other side deeper (the water is on a level, so all edges of the pond must be on the same level!);
  • Place a layer of 300 g/m2 non-woven fabric at the bottom (this prevents the liner from being punctured by roots or sharp stones);
  • On top of the layer of non-woven fabric lay the PVC or epdm liner over the shape of the excavation;
  • Fill the pond with water before fixing the liner to the edges. This ensures that the liner adheres perfectly to the shape of the pond without forming any gaps (which would put the liner under tension);
  • Once the pond is filled, you can fix the liner to the edges with pickets or stones;
  • If you want to perfectly camouflage the pond liner along the edges, you can follow our tutorial on how to make a perimeter niche for placing ground cover plants in moist soil;
  • Cover the edges of the liner around the pond by placing a round of stones or tuff and place some soil around the pond so as to cover well the liner that comes out of the edges of the excavation… and it’s done!

We have formed partnerships with companies producing pond liners and other materials for ponds or natural pools.

Here you can find liners and other materials for building your pond.


How to calculate the pond liner measurements

To get an idea of the pond liner measurements to purchase (and also in order to plan the excavation based on the available liner measurements), here are the formulas to use for a quick calculation:

Side A = A max + A1 + A2 + 2 * H max

Side B = B max + B1 + B2 + 2 * H max

When the excavation is complete, you can also calculate the measurements of the liner by fitting a metric wheel perfectly to the shape of the excavation. In this case, remember to extend the metric wheel an extra half meter on each side, where you are going to fix the liner externally.

Of course, the result must be rounded up according to the available liner size (usually one side of the liner must be a multiple of 2 meters).

Pond maintenance

The pond does not need any special maintenance work, except for pruning overgrowing plants in summer or at the end of winter before the plants awaken in spring.

If you place the appropriate aquatic plants (submerged oxygenating plants at the bottom, marsh plants on the edges, and plants with aquatic flowers such as water lilies and lotus flowers in the central area) you will succeed in having a “living” pond, in a natural and perfect balance , so you will not need filters, pumps and other mechanical equipment.

Water is filtered and purified by marsh plants and submerged plants, which, by releasing oxygen into the water, trigger the phyto-purification process.

Water purification occurs thanks to aerobic bacteria that live in symbiosis with the roots of aquatic plants. These bacteria are able to break down pollutants and organic substances that “foul the water” such as rotten leaves and fish excrement. The plants in turn feed on both the elements produced by the bacteria and the organic substances dissolved in the water.

The process that leads to a perfectly balanced pond normally takes about a year from the time you place the appropriate species and quantities of aquatic plants.

To learn more about how to have a naturally balanced and algae-free pond, download the free “Guide to Growing Aquatic Plants“.

In the following years you will probably remove the baskets to thin out the plants, or perhaps to add some more of them, but you will not have to empty the pond again, except in exceptional cases, because otherwise you would damage the ecosystem that has been created over time.

Now all you have to do is be proud of your work of art created in the garden and invite friends and family members to admire your beautiful pond!


This tutorial is also available in Italiano – Deutsch – Français – Español

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