Koi – Medium 20cm+-

Koi fish are ornamental variations of the common carp (Cyprinus carpio) and are recommended for larger ponds due to their large adult size (60 – 90 cm).  They are a hardy fish that does well in outdoor ponds.

The word Koi comes from the Japanese word for carp. Keeping and breeding Koi began in 19th century Japan when farmers kept colorful specimens of the native carp in their rice gardens. Now the keeping and breeding of these fish is a widespread and lucrative industry.

Behaviour

Koi are very peaceful fish that will interact with the others in their school while leaving that outside of their school alone.  They form schools of anywhere between 5 and 15 individuals and will swim in beautifully coordinated formations. Koi will visit every level of your pond. They will swim and dart along the surface and middle levels and forage for natural foods at the bottom. They are very active and free-swimming fish that will show off their vibrant colors at every opportunity.

Koi fish have a rather interesting way of hunting for food.  When foraging, they will dig and burrow into the sediment to uproot plants and munch on tasty seeds.  They eat like a vacuum, taking in big gulps of food and filtering out the dirt and mud.

Tank Conditions

In the winter, a heating system will be needed to prevent any freezing.  Water flow is not necessary, but the fish will be just fine if you choose to add a small stream or waterfall to your pond.  The pH of your pond should be kept between 6-9. You can use crushed limestone to your water can help to maintain your pH.

Your pond should be made from concrete, with a rubber lining and muddy bottom substrate.

The best plants for a water garden includes:

• water hyacinth
• water lilies
• cattails
• pickerels
• floating pondweed
• duckweed, and more

Koi need at least 1000 litres of water. A school of large Koi will require up to 4,000 litres.  The pond should have a minimum depth of at least 1.8 m and include both shallow and deeper areas. The rule of thumb with these fish is to keep 15 litres of water for every centimeter of fully grown Koi.  This means 1000 litres of water for one adult fish.

Compatibility

Goldfish are one of the most popular pond mate choices. They are similar in color and appearance and look beautiful when they swim alongside one another.  Other good pond mates include Catfish, largemouth bass and striped bass. Be aware that the bigger game fish will require a larger pond size.

Feeding

They are omnivores that eat seeds and plant material, algae, zooplankton, and insects. In a well-stocked pond, your fish will find vegetation and critters to munch on. The best diet for them includes an even mix of both natural and commercial foods.

They will readily eat algae and aquatic plants. You should keep a good stock of algae and floating weeds in order to discourage them from uprooting the plants in your water garden.

Rebel Pets has a full range of Pond Foods for Koi.

Care

The pH of your pond should be kept between 6-9. You can use crushed limestone to your water can help to maintain your pH.

Koi are susceptible to a fatal herpesvirus. Koi herpesvirus, or KHV, is a contagious virus that affects all varieties of the common carp.  Once a fish has been infected, there is an 80 percent chance that it will die from the illness. Symptoms of KHV include breathing difficulty, sunken eyes and red and white lesions at the gills. In many cases, the whole population must be euthanized once one fish is infected. KHV can be prevented by carefully inspecting the health of any new carp that you introduce to your pond. New fish should be quarantined for up to 2 weeks before you place them in your pond.

Other illnesses and parasites that affect Koi fish include fish lice, ich, and ulcerative diseases that affect goldfish and other carp. Watch for erratic or uncoordinated swimming, lethargy or breathing difficulty. Your fish will gulp at the air if it is having trouble breathing.

Even though these fish have a very high tolerance for poor water quality pond maintenance is the most important aspect of care and disease prevention.

Click for Fish Disease Diagnosis and Treatment at Rebel Pets.