Creating a Koi pond: Requirements for size and filter system + costs

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Creating a Koi pond: Requirements for size and filter system + costs: system

If you want to plant a koi pond in your garden, you can not ignore well thought-out planning. Because to keep the noble ornamental fish as appropriate to the species, the pond must meet certain requirements. In addition, Kois are relatively demanding, which is why the pond needs a certain basic equipment. What should be taken into account when creating a Koi pond and what costs can be expected? Find out here!


The noble ornamental fish have certain conditions to their habitat, so the siting is an important factor in the pond. First of all, it should be taken into account that the Kois need both shady and sunny spots. Ideally, the pond is thus one-third in the shade and two-thirds in the full sun. When choosing a location, the following aspects should also be taken into account:
  • Positioning of devices
  • Placement of external sockets for devices
  • 3m minimum distance between pond and power connection
  • Minimum distance to neighboring property
  • Planting around the pond
  • Seating, walkways, etc.
  • fuse
Note: Especially with children, securing the pond makes sense! If a child falls into the pond and injures himself, the pond owner is liable.


As a shade donor to offer in the home garden different plants, which is rather discouraged by deciduous trees. Because the falling leaves in autumn not only pollutes the pond, but also provides additional work. Instead, bamboo plants and Chinese grass or conifers should be cultivated in the immediate vicinity of the pond. Alternatively, the following aids and constructions are also suitable as shade dispensers:
  • awning
  • web
  • bridge
Tip: An integrated waterfall not only provides a visual highlight, but at the same time for a restless water surface. As a result, the sunlight is broken, so the light is incident at a different angle.

Materials and shape

Koi in the pond

The shape of the pond is basically the taste of the pond owner, however, a round or oval shape is always preferable to a square. On the one hand, sharp or pointed edges pose a risk of injury to the fish and, on the other hand, dirt can accumulate in the corners. However, the material that makes the pond the best depends primarily on the composition of the soil. For the Koi pond, the following materials are available:
emphasizes calibration
  • is suitable for sandy soils
  • Advantages: simple and robust, freely designable
  • is easy to clean
  • Disadvantages: pond edge must be laminated
  • Costs for the specialist company
liner pond
  • is suitable for clay or loam soil
  • Advantage: Relatively cheap and flexible
  • Disadvantage: prone to damage
  • Wrinkling in the film
  • dirt can accumulate in it
Glass reinforced plastic
  • Advantage: extremely durable and stable
  • corrosion resistant and insulating
  • Disadvantage: relatively expensive

Size of the pond

The size of the pond is crucial for the well-being of the Kois, because the Kois need enough space to live in an appropriate way. It is also important to keep in mind that kois are always kept in groups of at least 5 pieces. The pond size is thus directly dependent on the fish stock, with the following guide values:
  • at least 1,000 liters of water per koi
  • optimally 3,000 -5,000 liters of water per koi
  • each additional koi requires an additional 1,000 liters
  • 10 koi need around 15,000 liters
  • Koi pond at least 10-30 m³ volume
Note: From a certain pond size a building permit is required!

Depth of the pond

The pond represents the optimal habitat for the Kois, if it has both deep and shallow places. The Koi need a certain depth to hibernate in the lower water layers. The shallow places, however, are needed by the females for spawning. If the females do not have the opportunity to lay eggs, they reduce the eggs again, which can make them sick sometimes. It is therefore important that the Koi pond is not only large but deep as well:
  • Minimum depth: 1.5-2.0m
  • lower than 2.5 not advisable
  • Fish are otherwise difficult to catch


Water lily - dragonfly

In order to always ensure excellent water quality, it is advisable to equip the pond with some mechanical equipment. Because they not only clean the water from debris and dirt, but also enrich it with vital oxygen. Of course, not all equipment is an absolute must, but they help immensely to keep the climate within the koi pond always stable.In particular, a high-quality filter system is considered essential for many Koibesitzer and is therefore strictly recommended.
A filter is almost indispensable in the Koi pond, because the noble ornamental fish eat comparatively much. This in turn increases the amount of excretions that naturally pollute the water. The impaired water quality, however, affects the health of the fish and represents an enormous danger to them. In order to always ensure the cleanness of the water, the installation of a filter is usually necessary. There are different models, the best ones being:
chamber filter
  • mechanical and biological filtration
  • Advantages: Cost-effective and flexible
  • Disadvantages: often needs to be cleaned, large footprint
  • filters the water in up to 5 different chambers
  • Cost: from about 400 euros
  • biological filtration
  • Advantages: powerful and space-saving
  • Disadvantages: relatively expensive, energy-consuming
  • Filter chamber filled with tiny plastic balls (beads)
  • Cost: from about 600 euros
module filter
  • works like chamber filter
  • Advantages: adaptable and expandable
  • disadvantages: must be cleaned manually
  • Freestanding chambers can be added or removed
  • Cost: from about 600 euros
  • enriches water with oxygen
  • Advantage: cost-effective and space-saving
  • Disadvantage: only poorly integrated optically, relatively loud
  • Cost: from about 200 euros
drum filter
  • mechanical cleaning
  • Advantage: particularly effective, quiet and low maintenance
  • Disadvantage: high acquisition costs, large space requirement
  • Costs: from about 1,000 euros

Other equipment

In addition to the filter, a powerful pond pump is also essential. Because the pump sucks in the water, passes it to the filter and then back into the pond. When buying a pump, however, it must be ensured that the manufacturer's instructions usually refer to ponds with no or only a small amount of fish. To ensure that the pump is suitable for the planned pond size, the information should therefore always be halved or divided in half. If the basic elements are available, the pond can still be equipped with the following devices:
  • UVC device: Keeps the germ count low
  • Diaphragm pump: Provides additional oxygen supply
  • Pond Soak: Removes mud from the bottom of the pond
  • Skimmer: keeps the water surface clean
Tip: The equipment with different devices is advisable, but not mandatory. Especially for ponds with a low fish stock, it is possible to ensure the water quality and oxygen supply with sufficient planting.


Water Lilies - Nymphaea

When planting koi ponds, it is essential to take into account that the ornamental fish tamper with and nibble on most of the plants. For the koi pond, therefore, separate plant zones, such as a small creek with flowering plants, have proven to be particularly effective. Alternatively, so-called plant islands offer themselves: These float freely on the water surface and are provided below with a protective net and thus protected from the koi. If you would like to plant the pond, you should preferably choose the following plants:
  • Water Lilies
  • Hornblatt
  • bulrush


The cost of a koi pond varies greatly and therefore can not be generalized. On the one hand there is the possibility to create the pond itself and on the other hand this can be done by a specialist company. In the case of self-construction, only the material costs are incurred, whereas most specialist companies offer a price per 1,000 liters of water volume. A professionally executed pond planning can therefore fall with several thousand euros in the budget. In addition to the one-off acquisition costs, however, the ongoing fixed costs should also be taken into account:
  • Minimum volume 10,000 liters
  • from 30,000 liters: fixed costs x3
  • from 60,000 liters: fixed costs x9
  • Electricity costs: 30-150 euros / month
  • Water costs: 10-50 Euro / month
  • Food: 10-50 Euro / month


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