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related article: Outdoor Fish Pond
Numerous garden pond owners prefer Koi fish for their aquatic gardens. Koi are the Japanese national status fish and are called "nishikigoi". For that reason Koi ponds are often designed in Japanese water garden style.
Asian Koi fish, also known as Koi carps, show robust health, as long as you offer good care and conditions. They often get up to 35 years old. With perfect water conditions your Kois may reach a length of 60cm (24 inches) in your artificial pond. With their shiny colours of red, orange, white and black these fish are an enrichment for any water landscape.
If you intent to keep Koi fish in a garden pond, you have to provide a water depth of at least 1m (3.3 feet), but we advice a depth of 1,30m - 1,50m (4.2 - 5 feet). The first reason is that koi carps need lots of space to swim freely.
Second: You need this pond depth, so your Asian carps can hibernate without freezing to death in your garden pond. A water depth of 1m (3.3 feet) and more guarantees that a pond will not freeze through completely and hibernation of any pond life is not at risk during winter break.
Remember to clean the pond's ground from mud and biological rubbish. Kois need clear water that is rich of oxygen.
Koi carps in a garden pond like to socialize. So, if you start to populate your aquatic garden you should release at least 5 animals at once. Old and young carps need stability in pond conditions. Besides clear water you need to provide efficient circulation by pond streams or a waterfall to enrich water quality with oxygen. Who fills his backyard pond with tap water should use dichloride and control ph-factor. Try to get a pH-factor around 7 or 7.5 for your water acidity. Kind in mind that your Koi carps will need more oxygen and more space to swim around while they get bigger and bigger.
A Koi pond suffers more from natural excrements of its fish than a common fishpond. Take precaution by planting enough floating plants and underwater flora as well as by installing biological water filters. Clean the filters twice a year, even if your water appears to be clear. Under any circumstances avoid sudden, heavy fluctuation of water temperatures. This could kill your Kois. The range of water temperatures between 4°C and 28°C (39°F and 82°F) is acceptable for a healthy pond life.
You can build your own Koi Pond with flexible pond liner folia or with a preformed pond shell. Garden centre offer Fiberglass Garden Ponds, that are developed especially to keep Kois over the whole year. Those pre-manufactured shells come with an enormous pond depth and a much bigger pond volume than normal pond liner. You have to calculate about 1000 litre (230 gallons) per Koi to make sure that adult carps find enough space to move around. Most of these frost-free and weather-resistant fishponds already come with small pockets for all zones of your aquatic plants.
Be aware that a Koi carp likes to "jump". This can happen during breeding, if water condition suddenly change or just for fun. Keep this in mind when you plan to design and build a water garden of Koi carps.
Soon you will find out that Koi carps in a garden pond are very gentle animals. They eat nearly everything. You can enrich common fish-food with pieces of bread, pearl barleys or oats, but do not overfeed your pond fish. Unused food will sink and produce nutrients that will help Pond Algae to grow. According to the season you should feed your fish once or twice a day (1x in winter, 2x in summer). As soon as Japanese Koi are acclimatized in a healthy aquatic landscape they become trusting and may even eat out of your hand.
If one day your pond pump isn't working anymore, stop feeding, because Koi carp consume much more oxygen after eating. An Asian Koi fish is capable to survive 2 weeks without eating. Show responsibility to the carps in your water garden and provide healthy conditions with clean and clear water and a balanced water flora for all animals in your aquatic garden landscape.
If you tough your Koi fish during pond care or during periodically inspections for fish diseases, make sure not to wipe away the tiny layer of slime that covers the fish like a transparent mantle. This layer protects Koi Carps against bacteria and to fight fungus.