Swimming pond construction

Reading time 10 minutes

Updated – February 2, 2023

A swimming pond without filters, pump technology and still clean water, is that possible? Yes!

We have already built several ponds: a pond system in terraces of different heights (with a pump if you want waterfalls on the steps), also as a diving pool after the sauna or as a swimming pond with extensive shallow water zones.

Clear water

Clean water is ensured by plenty of plants at all depth levels, four different (schooling) fish species, some of which also eat the annoying mosquitoes and their larvae, but also dead plant remains, as well as pond mussels, each of which filters around 1 cubic meter of water per day.

With a volume of around 34 m² and 135 m² of pond liner, we used around 500 plants, as well as ten specimens each of softworms, groundlings, minnows and bitterlings, as well as four pond mussels.

The cleaning crew

Each type of fish has its own cleaning task:

Moderlieschen are 6 to 9 cm long, feed on mosquito larvae, algae, water fleas and hoppers, as well as mosquitoes that fly close to the water surface.

Basiclings are about 10 .. 14 cm long, feed on insect larvae and molluscs and crustaceans.

Minnows are about 6 to 10 cm long, feed on insect larvae, small crustaceans, algae and approaching food, and therefore stay in the upper layers of water.

Bitterlings are 6..9 cm long, require shells to reproduce and feed on algae and invertebrates.

The fish are multiplying quite well. Within six months, hundreds to over a thousand fish can have arrived.

It takes a few months until the water is clear enough to see the bottom. Only when the biological balance has been established will you be able to see the activity of the fish themselves on the bottom of the pond.

Algae growth

The formation of algae, which is often viewed with suspicion and fought with zeal, is a natural process, especially in freshly created ponds and in spring: the algae bind excess nutrients and disappear on their own (!) as soon as a balanced ratio has been formed.

The danger of mechanically removing algae from uprooting plants that are in the process of growing is great. This is another reason why this is not recommended.

Tempering

Heating in winter is only necessary in very small and shallow ponds in order to always guarantee the fish stock a frost-proof water temperature. In this case, it is advisable to integrate a water feature housed in a round mortar tub, with a heating cable on the bottom and switched via a temperature sensor. The pump should only run sporadically, for example controlled by a motion detector, so that the water in the tub is not circulated too much and there are large temperature fluctuations.

planning

At the beginning there should be thorough planning: shape and extent of the pond, depths of the individual zones and the maximum depth, as well as the design of the individual areas.

Particular attention should be paid to a so-called security level. This is an area that allows children and animals a safe exit to the mainland. It should be sufficiently wide and can also serve as part of the shallow water zone.

Deciduous trees, non-evergreen shrubs, etc. should be kept far away from the pond if you want to prevent leaves from constantly being added, which in the long term will lead to silting up of the pond.

The smallest area that can still be planted should not be less than 40 cm x length, otherwise they could slip. Natural fiber mesh mats, in which the plants can sink their roots and thus find solid support, help here for additional fastening.

Visualization of the shore

To visually represent the bank, you can use one or, depending on the size of the pond, several garden hoses. You lay it the way you basically imagine the shape and adjust it here and there until you find the shape you like.

Now you use the spade to cut this virtual bank boundary to the width of the spade.

Step contouring

Then lay the garden hose again to define the first stage. Here too, the spade is used in the same way.
Proceed in this way until all depth zones have been demarcated.

Excavations

Now it's time to dig, by hand, which takes time, but gives muscle and in this way saves the gym, or with heavier equipment, such as (mini) excavators. The deepest zone is dug first, then the next, until you reach the top of the last one.

Slide plan

Now draw the pond roughly according to its shape on an A4 sheet, including a “north” mark. Then you draw a line through the imaginary longitudinal center of the pond, next to which you enter the dimensions required for the pond liner to be ordered. As a fixed point for film production, mark the corner where there is the most space in the area.

Latitude...

A garden hose is laid out on this imaginary center line of the longitudinal axis. Using a sufficiently long tape measure (50 m) that fits neatly onto the steps, the resulting length from the left to the right edge of the pond is determined every 50 cm, starting from the far edge of the pond, for example, at right angles across this center line. The lengths found in this way are entered one below the other next to the drawn center line on the dimension sheet.

A clear (video) Instructions can be found on the Naturagart website, which has been dedicated to pond building for over thirty years and has developed what we believe to be the best method of pond building.

... and longitude

The length of the pond is determined in the same way. Here you add around 80 cm above and below, so add 160 cm to the measured distance.

Economics of custom-made production

Natural agart® welds the film according to this dimension sketch. There are also standard dimensions. If you don't prefer a rectangular or square pond, but rather a natural pond shape, you will have to accept a lot of waste.

Layer structure

After excavating the soil, stones and roots (at least 20 cm long) are removed, hollows are leveled, and walls and surfaces are made clean and level.

First layer – silo film

Silo film of suitable dimensions is applied as the first layer. It serves as weather protection, prevents washing out in heavy rain during the construction phase and creates a clean working environment when laying the pond fleece that protects the pond liner.

Second layer – pond fleece

This slide will Pond fleece placed as a second layer. There are different versions that differ in their strength and properties. Of course, as is usually the case, more power also costs more money. In addition to protecting against penetrating roots and sharp stones, Naturagart® fleeces have the extremely pleasant and valuable property of being “self-healing” in the event of an injury to the pond liner. They seal the foil hole from below by allowing sediment to penetrate. However, this should not lead you to use hardware store qualities for the film.

Third layer – pond liner

The heart of the pond is the pond liner. Special attention should be paid to it: here you should take advantage of the Foil assortment choose from Naturagart. The tendency to save money here is understandable given the prices for a high-quality and durable film, but it is by no means advisable. After all, this film decides the success or failure of the entire pond venture!

Folds are removed by cutting with an overlap of 6 to 8 cm in order to be able to weld them well and to obtain a largely homogeneous surface.

Custom-made production avoids this waste, which means significant savings.

Laying the pond liner

Here too, Naturagart® has a very good one Video instructions provided, from which the individual steps are clearly comprehensible.

With our pond, we had concerns about whether we could handle the 135 square meter pond liner with four people. But it was actually as easy as it seemed in the Naturagart® videos.

Preparations

The surrounding edge of the pond should be free of unevenness, tools, etc. to ensure unhindered movement around the pond.

The film is delivered on a pallet, welded together in strips according to the dimensions. The location of the pallet corresponds to that on the sketch made with the strip dimensions and the fixed point specified on it, just under one meter from the edge of the pond. A mini excavator equipped with appropriate lifting equipment should be available to position the pallet.

positioning

From here the film is unrolled from the pallet and across the width of the pond. The film should now extend equally over the largest width of the pond on the right and left. If necessary, the position needs to be corrected by moving it. Ultimately, the film roll should lie straight and without any kinks. The end of the film ideally lies on top or is positioned so that it is easy to grasp.

Let's go

Now grab the two top ends of the foil on the right and left with both hands, lift them to waist height and courageously pull the foil over the pond. Other helpers grab the edge of the foil closest to them and, also walking towards the end of the pond, pull along to support them.

The faster you pull the film over the pond, the easier it is: the film covers the air underneath and glides smoothly along this air cushion. You can first practice the process in a test run so that you don't fall over any tripping hazards later and the film then sinks to the bottom of the pond.

Just in case

If the mishap does happen, the first helpers have to move the foil up and down rhythmically in synchrony and in this way bring air under the foil. The helpers distributed around the edge follow the up and down according to the air cushion wave created under the film. If the foil finally floats again, you continue pulling together to pull the foil completely over the pond.

Fine work

Once the film is in place, it is important to smooth out the wrinkles and fold the corners as neatly as possible. This procedure is repeated continuously while filling with water, because once the film has water on it, it can no longer be moved.

Fourth layer – shore mat

Like the pond fleece before, this will also be the case shore mat built-in. Bank mat serves as a rooting space for plant roots, especially on sloping pond edges.

The shore mat is best glued with the, albeit expensive, but unbeatable K1 all-purpose glue, underwater adhesive agent that is delivered in cartridges and applied using standard cartridge presses. Even products sold as industrial adhesives do not stick to the pond liner, as we had to learn the hard way before we ordered the K1 adhesive again.

Folds are removed again by cutting to fit, overlapping by approximately 6 to 8 cm.

Fifth layer – option

As a fifth layer, we laid out remaining pieces of the pond fleece in the entry and exit areas to prevent damage to the liner caused by dog claws. They were glued directly to the pond liner.

Naturagart® also suggests the possibility of a “Armor“ of the pond liner by applying a layer of mortar. It serves to increase resistance to mechanical stress, such as animal claws. However, you should pay attention to the special material concerns and special ones Pond construction mortar use.

Welding the fleece and bank mat strips

The overlaps of the pond fleece and the shore mat are welded together with an overlap of approximately 6 to 8 cm using an adjustable hot air blower (50 to 650 °C). This results in a uniform and continuous “tub”.

The Leister® company offers suitable devices for this. There are also cheaper ones, but ours has it Leister Solano AT convincing both technically and in terms of working ergonomics. You also need one that is angled at 15° Wide slot nozzlein order to bring the hot air, which is set to 250 .. 350 °C, ergonomically and effectively between the fleece layers, depending on the wind and outside temperature.

Welding is carried out quickly by holding the device with the handle upwards in one hand and inserting the nozzle, which is mounted at an appropriate angle, parallel between the two layers of fleece. Now pull the device along the seam at a constant speed and press the upper fleece firmly onto the lower layer with your free hand. In this way, the surfaces of the fleeces that melt due to the hot air permanently bond to one another.

Cutting work

A good pair of scissors is enough to cut the bank mat. However, pond fleece, especially in the overlapping areas with a thickness of almost 2 cm, requires good motorized scissors if you don't want to risk having to use new scissors every few meters, blisters on your hands, etc. Thick fleeces in particular can no longer be handled manually. The RASOR Optima 703 is, for example, a suitable device.

Equipment purchase or rental

If you are not planning to build several ponds, we recommend renting these rather expensive devices instead of buying them. If you are interested, please send an email teichbau@csiag.de send.

Pond equipment

Before it's called “Water March”, a few cubic meters of unwashed sand are needed. The soil layer should be a good 10 to 15 cm, as should the bank zones, in order to have enough space for the root balls of the plants. You can roughly calculate the amount required by multiplying the area by 0.1...0.15.

After the sand has been applied to the appropriate thickness everywhere, water can be added until the deepest layer of sand is just covered with water. To avoid washing away the sand in the area of the water hose, it is best to use a spray jet.

planting

Like the fish, so have Plant not only have an aesthetic benefit, but primarily serve to create a good nutrient balance in the water. Here the advice of the biologists and botanists at Naturagart® is worth its weight in gold. A phone call in advance provides the first helpful clues for your own preliminary planning.

The final planning should be left to the experts at Naturagart. They are based on the sketch that has already been made with the marking “North”, the communicated wishes regarding high or low vegetation and, if necessary, premises expressed regarding plant species, etc. The proposal you then create includes a compilation and localization of the various plant species that are based on solar orientation, nutrient availability, depth, etc.

Depth zone

The deep-water plants are first planted in the sand layer of the pond bottom that is just covered with water. Always loosen the root balls a little and then insert them into the sand and press them down. The filling then continues again up to the next level covered with sand. Now this level is populated with the plants intended for this depth range. Continue like this until all levels have been planted.

Edge of the pond

Naturagart offers a sophisticated aluminum profile system for edge fastening. Alternatively, as we did, there is a cheaper option PVC lawn edging at. It also offers good durability and a sufficiently wide edge to use a spirit level to create a horizontal alignment, which can ultimately be used to orientate the film edge and thus the water surface.

Finally, we glued the film to the edge of the lawn in the entry and exit areas after the pond had had six months to “set” and the film would no longer be expected to sink and therefore tighten in the future.

If there is sufficient planting and, if necessary, surrounding lawn, the artificial pond boundary becomes blurred. This creates the impression of a natural pond biotope.

Gimmicks

If you want to integrate lighting, fountains, thick boulders, etc. into the pond, you should of course take these into account before planting. Cables are laid under the sand, or better still under the bank mat, towards the edge of the pond and routed outside the pond to the electrical distribution.

Heavy decorative stones/boulders should be given a layer of the thickest pond fleece, which can withstand several tons of load and effectively protect the pond liner. Insertion using an excavator shovel is carried out with great sensitivity from the edge before it is finally shaped and attached.

Bathe

Before the first bathing can take place, the plants should be given sufficient time to develop roots and anchor themselves firmly in the sand. You let the first year pass as a time of anticipation so that in the second year you can finally enjoy the joys of bathing without regrets. Nevertheless, you should use gentle swimming strokes and not immediately crawl and rinse the delicate roots of plants that are closer to you.

Filter ditch – alternative to fish stocking

Narturagart® has developed the principle of the filter trench to perfection. A circulation pump sucks at the far end in a so-called sediment trap settled water-sediment mixture and directs it into the filter trench. The sediments settle there. Plants with high nutrient requirements remove nutrients from the sediment and nutrient-rich water and in this way keep the water in the pond clear. It can be periodically flushed via a pressure line connected to the sediment trap.

However, this solution has one disadvantage: mosquito larvae remain on the water surface and the edge of the pond, just like in the wild. There are chemical agents that cause mosquito larvae to die, but if you want to build a biotope, you might prefer to use natural agents, fish.