Planning a swim pond – important information on approval, fish & care

A swimming pond is not built quickly. Without the right planning, the project can quickly fail and, in the worst case, even result in high fines.

Swimming ponds combine the beauty and ambience of a pond or biotope with the advantages of a swimming pool. The natural alternative to swimming pools is self-cleaning and does not depend on chlorine and other chemical agents.

At the same time, of course, there are a few things to consider when creating the pond, which are essential for a long-term intact pond. If you pay attention to a few important things before building, you will save a lot of time and unnecessary work.

Do I need a permit OR Planning Permission

Many people are not aware that ponds often require a permit. However, because ponds that have not been reported can lead to warnings and fines, you should definitely have your pond approved in advance. In most federal states, this is necessary from a water depth of 1.5 meters and a total volume of 100 cubic meters. Here it depends a lot on the state.

In many areas, even the smallest ponds have to be registered. If you build a pond there in a local area, this must be registered immediately. Especially with swimming ponds, you should play it safe and get detailed information in advance.

Structure of the pond

The pond should be built up over several levels so that it is in an ecological balance at different temperatures and weather conditions. This is especially important in warmer temperatures, when the lower levels protect the pond from an algae bloom, lack of oxygen, and an increase in nitrogen and phosphorus. So it makes sense, especially in warmer areas, for example, southern Germany, to dig a pond depth of 2 meters or more.

In the case of larger ponds, it can easily happen that the pond liner is cracked or has holes in the bottom due to sharp stones. To avoid this, it is best to dig the pond 10 centimeters deeper than originally planned and then pour a 10-centimeter high layer with small pebbles. This protects the pond liner and also looks more natural. Such work can be very time-consuming and exhausting. If you want to save yourself the work, you can also outsource it. On portals like Renovero, you can find qualified craftsmen with pond construction experience without a long search. In the meantime, you can deal with other things again, such as pond technology.

Technology in the garden pond: is a water filter necessary?
In principle, garden ponds do not require any technology as long as the nutrient concentration remains at a moderate level. The larger the pond, the easier it is to keep the water in balance. If you have a small pond, it can help to install a filter system that is activated when necessary. This can reduce the algae, especially in hot temperatures. It also filters toxins, suspended matter and excess fish food out of the water.

Fish in the swimming pond

Fish and water dwellers are often a particular challenge because they can easily cause a balanced body of water to tip over with faeces and leftover food. Especially when the water tends to rapid algae growth and a lack of oxygen due to warm temperatures.

Less is more should be the motto when buying the fish in order to be able to guarantee the health of the pond. One should calculate generously, especially because young fish will often multiply their size in the coming years. The experts at Gartenteich-Ratgeber recommend planning around 600 liters of water for a fish with a fully grown length of 25 centimeters in order to be on the safe side.

Basically, fish are not part of the pond’s ecological cycle, which is necessary for long-term balance. Rather, fish are a risk factor that can easily become fatal. This is especially the case with smaller ponds.

The more fish in the pond, the more technology is required to keep the water in balance. One should also pay attention to the menu of the pond dwellers. Kois or goldfish, for example, like to eat the underwater plants, which as a result are unable to displace rising algae. Other species, for example, carp or certain koi races, also eat the algae and create an opaque green in the water that makes it difficult to observe fish from outside.

Risk of over-fertilization

Probably the greatest danger in ponds is over-fertilization. It increases significantly when fish are kept. Fish, algae and fish food make the water too rich in nutrients and threaten to tip over. Keeping a lot of fish in a limited pond is particularly dangerous. Then about 10-20 percent of the water should be replaced every week in order not to keep too many nutrients in the water.

Correct position of the pond

Where would you like to dig your garden pond? The water is often the showpiece of the garden and is therefore often excavated in particularly clear places. It is important, however, not to let too little or too much sunshine on the pond. Five hours of sunshine are ideal for plant growth, but it shouldn’t be much more. Sun protection for the pond can therefore make sense under certain circumstances.

Important: Shallow roots with hard roots should not be allowed to thrive near the pond, as they can be a danger to the pond liner.

Pond maintenance: The perfect pond rarely runs on autopilot

Having a pond means taking responsibility and taking appropriate care. Especially when fish are involved. This includes, for example, regular checking of water values: What is the pH value of the water? How much phosphorus and nitrogen trioxide do you find in water? What is the total hardness? The garden pond professional Tetra explains in his guide which individual water values ​​are important and how they should turn out.

Even if you do not use technology at all, there is always work to be done – for example, a proliferating water plant can quickly fill large parts of the pond. In this case, you need to act quickly and remove them.

Even in winter, you are often confronted with challenges. You have to ensure that the swimming pond remains free of ice so that there is enough oxygen for the pond inhabitants. For example, ice preventers are suitable for this:

An air pump or an oxidizer for the oxygen supply can also have a positive effect.


A swimming pond in your own garden can be a lot of fun and is basically low-maintenance. The interplay of water and the right plants around it is particularly beautiful to look at. Nevertheless, one should not underestimate the effort. The pond must be watched, especially in extreme temperatures. If you also keep fish in the swimming pond, the pond’s ecosystem is much more sensitive, and the use of technology such as air pumps and water filters is particularly recommended. Overall, building a swimming pond is not rocket science, but it takes time and effort so that you can enjoy your swimming pond a lot.

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