Planning a swimming pond – Important information on permits, fish & care

A swimming pond isn’t even built fast enough. Without the right planning, the project can quickly fail and in the worst case even result in high fines.

Planning a swimming pond
Pond and pool in one: the swimming pond! © La Vas –

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

At the same time, of course, there are a few things to consider when creating the pond that are essential for a pond to remain intact in the long term. Those who already pay attention to some important things before the construction save a lot of time and unnecessary work.

Is a permit required?

Many people are unaware that ponds often require a permit. However, because undeclared ponds can lead to warnings and fines, you should have your pond approved in advance. In most federal states, this is already necessary from a water depth of 1.5 metres and a total volume of 100 cubic metres. Here it depends strongly on the federal state. The experts at MCM Systeme have prepared a table showing which legal bases exist in the individual federal states and what additional legal requirements must be observed during construction.

In many areas, for example in neighbouring Austria, even the smallest ponds have to be registered. If you build a pond there in a local area, it must be registered immediately. Especially with swimming ponds you should play it safe and inform yourself in advance.

Structure of the pond

Planning a swimming pond - Construction
© white78 –

The pond should be built up over several steps so that it is in an ecological balance at different temperatures and weather conditions. This is especially important at warmer temperatures when the lower levels protect the pond from algae bloom, oxygen deficiency, nitrogen and phosphorus increases. It therefore makes sense, especially in warmer regions such as southern the United States, to excavate a pond depth of 2 metres or more.

With larger ponds it can easily happen that the lined pond liner gets cracks or holes at the bottom through pointed stones. To avoid this, it is best to raise the pond 10 centimetres deeper than originally planned and then pour a layer of small pebbles about 10 centimetres high onto it. 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 will find qualified craftsmen with pond construction experience without a long search. In the meantime, you will be able to deal with other things again, such as pond technology.

Technology in garden ponds: Is a water filter necessary?

In principle, garden ponds do not require any technology as long as the nutrient concentration remains moderate. The larger the pond, the lighter the water remains in balance. If you have a small pond, it can help to install a filter system, which is activated if necessary. Especially at hot temperatures this can reduce the algae. In addition, toxins, suspended matter and excess fish food are filtered out of the water.

Fish in the swimming pond

Planning a swimming pond - Fish
© JFsPic –

Fish and water dwellers are often particularly challenging because they can easily tip over a well-balanced body of water with excrement and food leftovers. This is especially the case when the water already tends towards rapid algae growth and oxygen deficiency due to warm temperatures.

Less is more should be the motto when buying fish, in order to guarantee the health of the pond. Especially because young fish often multiply their size in the coming years, one should calculate generously. The experts from Gartenteich-Ratgeber recommend planning around 600 litres of water for a fish with a full-grown length of 25 centimetres in order to be on the safe side.

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

In a nutshell:
The more fish in the pond, the more technology is needed to keep the water in balance. One should also pay attention to the diet of the pond inhabitants. Koi or goldfish, for example, like to eat the underwater plants, which as a result cannot displace algae that have risen as a result. Other species, such as carp or certain koir breeds, also eat the algae, creating an opaque green in the water that makes it difficult to observe fish from the outside.

Risk of eutrophication

The probably biggest danger with ponds is the overfertilization. It increases significantly when fish are kept. Fish, algae growth and fish food make the water too nutrient-rich and threaten to tip over. Keeping many fish in a pond of limited size is particularly dangerous. Then about 10-20 percent of the water should be exchanged per week in order not to keep too many nutrients in the water.

Correct position of the pond

Planning a swimming pond - location and location
© white78 –

Where would you like to dig your garden pond? The water often represents the showpiece of the garden and is therefore often excavated in particularly bright places. But it is important not to let too little and not too much sun shine on the pond. Five hours of sunshine are optimal for plant growth, but it should not be much more. Sun protection for the pond can therefore make sense under certain circumstances.

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

Pond care: The perfect pond rarely runs on autopilot

Having a pond means taking responsibility and providing appropriate care. Especially when fish are involved. This includes the regular checking of water values: What is the pH value of the water? How much phosphorus and nitrogen trioxide can be found in water? What is the total hardness? The garden pond professional Tetra explains in his guidebook which individual water values are important and how they should turn out.

Even if technology is not used at all, there are always jobs to do – for example, a proliferating aquatic plant can quickly fill large parts of the pond. In this case, you must intervene quickly and remove them.

Even in winter you are often confronted with challenges. So you have to make sure that the swimming pond remains ice-free so that enough oxygen remains for the pond inhabitants. Rustikal, part of the ice can then be chopped off. Alternatively, you can install an ice separator.

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

bottom line

A swimming pond in your own garden can be a lot of fun and is basically low-maintenance. The interaction of water and the right plants around it is especially beautiful to look at. Nevertheless, the effort should not be underestimated. Especially at extreme temperatures the pond must be kept in mind. If you keep additional fish in the swimming pond, the ecosystem of the pond is much more sensitive and the use of technology such as air pumps and water filters is particularly recommended. All in all, building a swimming pond is not a witchcraft, but it takes time and effort so that you can enjoy your swimming pond to the full.

Don Burke

I am Don Burke, one of the authors at My Garden Guide.  I am a horticulturist that cultivates, grows, and cares for plants, ranging from shrubs and fruits to flowers. I do it in my own garden and in my nursery. I show you how to take care of your garden and how to perform garden landscaping in an easy way, step by step.I am originally from Sydney and I wrote in local magazines. Later on, I have decided, more than two decades ago, to create my own blog. My area of specialization is related to orchid care, succulent care, and the study of the substrate and the soil. Therefore, you will see many articles dedicated to these disciplines. I also provide advice about how to improve the landscape design of your garden.

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