What is required for a koi pond

Building a koi pond: Tips for setting up and maintaining it

In order to build a koi pond yourself, you should do some research beforehand. Kois are not only particularly beautiful and calm fish, they are also very demanding in terms of keeping and care. Under no circumstances should you simply put the valuable ornamental fish in a conventional garden pond, as the animals will not survive that for long.

Kois - or Nishikigoi (Japanese for brocade carp), as they are called by their full name - are all the rage and more and more people are bringing Japanese ornamental carp into their homes. If you want to keep the trusting fish as pets, there is no avoiding the construction of a spacious koi pond, because the animals up to one meter long and weighing around twenty kilograms are not suitable for living in an aquarium. If you want to build a koi pond, you should be aware that this is a large-scale and long-term project - koi carps can live up to sixty years old if they are well kept. In order to keep koi in a species-appropriate manner, a larger group of at least five animals is also necessary, because koi carp live in associations. The agile fish need around 1,500 liters of water per head to stay healthy and grow to their full size.

Building a koi pond: planning

The biggest difference between a koi pond and a traditional garden pond is probably its size. Both area and depth are important factors for the large fish to feel comfortable in their habitat. Make sure you plan a pond with sufficient water capacity for your koi. With five fish that means at least 7,500 to 8,000 liters of water. Since the fish overwinter in the pond, the water depth must be sufficient so that there are frost-free areas in which the animals can stay close to the ground even in the cold months. We strongly advise against hibernating in an aquarium in the house, as this means a lot of stress for the animals: There is a risk of disease and even the loss of the valuable koi. With a water depth of around 1.50 meters at the deepest point, you are also on the safe side in our latitudes.

Tip: The fish only need a small area for wintering, so the whole pond does not have to have the same water depth, as long as you plan in sufficient wintering zones to match the planned fish population.

The pond size will take up about thirty square meters in total - a koi pond is therefore not an acquisition for a small garden. If you choose a place for your koi pond that is neither fully in the sun nor fully in the shade, the water temperature will most likely remain constant. Ideally, this is around 15 to 18 degrees Celsius in spring, between 20 and 25 degrees Celsius in summer and over four degrees Celsius in winter.

Tip: If you plan to build a koi pond in your garden, think about an appropriate insurance, because the pond owner is liable in the event of damage.

Build a koi pond: pond tub or pond liner

The easiest way to build a koi pond is with a finished pond tray made of fiberglass-reinforced plastic, which you can get from specialist retailers. The scope, depth and capacity are already defined here. Special companies also manufacture the tubs according to their own dimensions on request. However, prefabricated ponds of the required size are very expensive and therefore may not be for everyone. If you want to design your koi pond inexpensively, you have to use pond liner. This also gives you much more leeway in terms of shaping and design. Since koi are valuable fish and the construction of a koi pond is no small matter, it is advisable to have the dimensions approved by a professional.

Tips: Do not plan too many curves and edges in a foil pond, as this makes laying the foil very difficult. Many small creases in the film should also be avoided, as dirt collects in them. When calculating the size of the pond liner, you need to factor in both the steps and arches and the overhang for the capillary barrier.

Build a koi pond: dig a pond pit and smooth the pond floor

The pond pit is excavated with a mini excavator and the various levels are designed. When calculating the depth, take into account that a cushioning layer of sand, a root protection film or a pond fleece as well as the inflow and outflow pipes must be drawn in between the membrane and the ground. You should also plan to dispose of the excavated material, as this adds up to a few cubic meters.

The pond floor is smoothed and all roots, stones and any debris that may have been excavated is removed. After laying and covering the pipes, the sand layer is put in, the pond fleece and liner are laid and the drain is installed in the ground.

Build a koi pond: fill it with water

If pond basins or liner are installed, the basin is slowly filled to about two thirds with water. After that, the entire construction should sag for a few days. During this time, the tightness is checked and the pump circuit is tested. Then the full water level can be let in. In order to prevent the pond water from seeping away from the edge of the koi pond into the garden, you should now construct a capillary barrier from the excess pond liner around the pond. Wait a few more days before finally cutting off the remains of the film until the film has settled and it is ensured that the pond is functional and tight.

A suitable filter system

Natural planting, which filters the water and brings oxygen into the biotope, ensures optimal water quality in the koi pond. In addition to natural water purification, one or more filters are recommended for koi ponds, depending on their size, so that the pool does not become muddy with excrement. The selection is large: there are chamber filters, bead filters, trickle filters, drum filters and many other systems. It is best to get advice on this from a specialist retailer. A skimmer is also a must to catch leaves and dirt floating on the surface. When planning, consider that the filters or pumps, depending on the type, may be placed around the pond at pond floor level and that appropriate pits must also be dug for this. In addition, the power supply must be ensured. According to the filters used, the piping is created and an inlet and outlet are installed.

Planting the koi pond

Before you start planting your koi pond, we advise you to draw up a planting plan. Think about the exact placement of the bank and aquatic plants as well as the required amount. When planting, it is better to use robust plants, because very tender species quickly fall victim to the hungry koi. High bank plants such as bamboo, cattails and other ornamental grasses provide a natural border. Aquatic plants such as water lilies filter carbon dioxide and suspended matter out of the water and bring in oxygen. Floating plants are important for shade, as koi with their light skin tend to sunburn. The fish can hide and rest under the leaves of the floating plants.

The maintenance of the koi pond is largely based on normal pond maintenance. Regularly skim off leaves and algae, cut back the water and bank plants and change the pond water every year.

Tip: A very thin, almost invisible, close-meshed net that is stretched over the pond protects the pond from falling leaves and the fish from cats, wild animals and herons.

Do not overfeed the koi as the carp are always hungry and only stop eating when there is no more food available. Regular checks of the water quality, pH value, oxygen content and various other values ​​are also part of the Koi pond care. During the hibernation you should neither feed nor disturb the fish in any other way.

Practical video: Creating a mini pond for the garden and balcony

No space for a large pond in the garden? No problem! Whether in the garden, on the terrace or on the balcony - even without fish, a mini pond is a great asset and provides holiday flair on balconies. In this practical video, we will show you how to put it on correctly.

Mini ponds are a simple and flexible alternative to large garden ponds, especially for small gardens. In this video we will show you how to create a mini pond yourself.
Credits: Camera and Editing: Alexander Buggisch / Production: Dieke van Dieken