What could be more relaxing than sitting outdoors on a (warm) summers day looking out on a beautiful Koi garden pond watching them swimming about? The key to a koi garden pond remaining a beautiful tranquil feature is good filtration, which is important for water quality and the health of fish. For those who are going to keep koi, the best possible conditions need to be provided to keep them healthy all year round.

If you are intending to build a pond in your garden to keep koi fish, there are some points you need to bear in mind:

• Koi can grow to 30 inches (75cm) when grown in good conditions – so avoid overcrowding your pond as it will risk causing problems to the health of your fish
• Large filter systems are essential which will take up further garden space
• Koi are warm water fish that thrive in temperatures above 20°C . Fluctuating water temperatures may result in fish loses. Water temperatures are more likely to be kept stable in larger ponds and ones located where it benefits from direct sunlight – however, this is coupled with the risk of algae bloom (treatable with an ultraviolet light clarifier).
• Koi need a stable environment to thrive. You need to provide a stable environment with a regular routine that is not stressful to koi inhabitants
• A protected electricity supply is needed to run a pond pump, and perhaps also water heaters, ultraviolet light clarifiers and lights.
• Good water circulation is essential to ensure good water quality, which is important for the well being of koi fish – the shape of a pond has an important impact on efficient water circulation.
• Koi are frightened when the pond they are swimming around in is approached by humans or predators and will instinctively try to escape to the point furthest from the point of threat. Ponds with sharp corners could result in fish being trapped or colliding with the wall of the pond.

Much to consider, but planning is vitally important particularly as constructing a koi garden pond is an expensive task. 

Koi garden pond size 

A Koi garden pond needs to provide clean, well oxygenated water and a healthy environment for fish to thrive and grow. A pond designed to home Koi needs to be large enough to accommodate the potential size that they can grow to ( 60cm or larger). 

Aim for a minimum pond size of around 2.5m x 2m x 1.2m deep (8 feet x 6 feet and 4 feet deep) and water volume of 550 litres or 1200 gallons. The larger the pond the less the fluctuation in water temperature. Koi are cold blooded and their body temperature matches the temperature of the pond. Sudden changes in temperature will cause physical stress and may lead to disease.

The stability of the water temperature is also affected by the ratio of surface area to volume. A deeper pond will be less affected by temperature fluctuations. Ponds with a good depth also offer greater opportunity for fish to swim about more freely.

Related articles on Koi garden ponds 

Box welded pond liners 

Calculating the water capacity of a pond