9 typical koi diseases with pictures

Koi are among the popular ornamental fish that create a calm and balanced atmosphere in the natural pond. So that this positive energy is not disturbed, the right posture is of great importance. Incorrect feeding and unsuitable living conditions lead to the outbreak of diseases.

signs of illness

Koi are social carp fish that are kept in groups. The number of animals in a tank depends on the size of the pond. It is of great importance for health, because incorrect housing conditions can cause various diseases. However, newly introduced fish can also introduce bacteria, viruses or parasites unnoticed. Diseases are often recognizable by a changed behavior of the koi.

• constant stay at the fresh water inlet
• exclusion from the school of fish
• jerky swimming
• horrible behavior
• staying on the water surface
• jumping out of the water

Ichthyophthirius

It is one of the most common koi diseases. Ichthyophthirius multifilis is a unicellular parasite spread by infested fish. The ciliates attach themselves to the mucous membranes on hidden parts of the body. They settle under gill covers, where they multiply rapidly and spread over the entire body. The first signs of a parasite infestation can be behavioral problems. Fish rub against stones to rid themselves of the parasites. They react by pinching their fins. While the microscopically small animals sit on hidden parts of the body, they cannot be fought directly. The parasites swimming freely in the water are killed with the active ingredient malachite green oxalate.

clinical picture

A disease is usually only noticed at an advanced stage, when the parasites leave white dots on the fins and scales. In the untreated course of the disease, whitish to yellowish spots appear that spread over the entire body. If more than a third of the mucous membranes have been damaged, the fish will die.

• all koi can contract Ichthyophthirius
• affected fish must be treated in quarantine
• Parasites usually multiply undetected and extremely quickly

Costia or Ichthyobodo

This disease is caused by the widespread parasite Ichthyobodo necator caused. This one is also under the name Costia neatrix known, which is now considered obsolete. In many cases, it is difficult to diagnose in the early stages, since the parasites live in hidden parts of the body and do not always spread over the entire body. The fish try to get away from the parasite with rocking movements. The signs become clearer as the pathogens spread. They cause bloodshot spots on the head and skin. Some of the spots are thickened with mucus. A thin coating may form that covers the body like a veil.

treatment measures

At the first signs, quick action is necessary to cure the disease. The parasites are killed with drugs. A preparation with the active ingredient acriflavin is dissolved in the water. In addition, oxygen should be added to the water. The fish should be quarantined. Increasing the water temperature to 30 degrees Celsius is only possible with warm-water fish. If the disease is not treated, the parasites destroy the mucous membranes. They let the fish disintegrate like shreds.

• Koi in winter ponds are affected more often
• Parasites do not necessarily spread to all fish in the pond
• Ichthyobodo parasites are dry tolerant
• can get back into the water through dirty landing nets

carp lice

Argulus foliacaeus is a native species belonging to the order Crustaceans. The parasite is up to 13 millimeters long and has suction cups and barbs with which it anchors itself in the fish skin. He stabs the tissue with his mouthparts and injects a bleeding-promoting venom. The cell tissue around the puncture site decomposes, so that more viruses and bacteria can get into the fish organism.

A transmission of other pathogens can take place when the carp lice suck blood. Spring viremia or koi herpes viruses often occur as secondary diseases. The parasites are fought with the help of drugs that are added to the water.

• high-quality feed mixtures strengthen health
• vital fish recover more quickly from an infestation
• Bodies of water should be monitored regularly
• occasionally birds can spread carp lice

swim bladder infection

This disease is caused by sporozoa caused. These spores live parasitically and settle in the gastrointestinal tract or in the body cavity. After an infection, the koi shows behavioral problems. Its activity is drastically reduced. It lies sideways on the pond floor or floats under the water surface in this position.

Early detection increases the chances of a complete cure. The affected koi are caught with a koikescher and placed in a tank with warm and well-aerated water. The pool should be shallow. The fish should remain here until they have recovered.

• young koi are more susceptible
• greatest risk of infection in the first year of life
• Fish recover in a suitable environment without medication

Infectious Ascites (IBW)

Various causes lead to the onset of this disease. It can be caused when a koi ingests viruses and bacteria through water or food. They get into the gastrointestinal tract and change the faeces. The first signs are bloodshot and protruding scales, so that the koi looks like a dried out pine cone. The entire body is swollen, so the eyes are prominent. It is difficult for the fish to breathe. He swims sluggishly in the water and struggles to stabilize himself. An illness usually ends fatally within two days, because in the course of the illness the intestinal mucosa dissolves and is excreted with it.

• typical are goggle eyes
• slimy white feces
• inflammation of the anus
• blistering under the skin

The infectious disease is highly contagious. The affected koi should be quarantined as soon as possible and treated with antibiotics. The earlier the disease is noticed, the more likely it is that the treatment will be successful. In the late stage, the internal organs can already be severely damaged.

• Bacterial disease often occurs as a secondary disease
• weakened koi are more susceptible
• Bacteria can be present in contaminated food

erythrodermatitis

This infectious bacterial disease occurs under poor husbandry conditions. It manifests itself as smooth-edged or white-edged sores or holes on the skin. The ulcers are often deep red in color. Once the disease is noticed, the fish should be treated with antibiotics or sulfonamides. In the early stages of the disease, the infection can be cured. If the bacteria have penetrated to the body cavity, healing is no longer possible in most cases. If left untreated, the disease ends fatally.

• Bacteria mainly attack scaleless koi species
• The disease only occurs when there is a fault in posture
• improved husbandry conditions curb the disease

spring viremia

This disease is the acute form of infectious abdominal dropsy. In contrast to IBW, spring viremia is triggered by viruses. Affected koi show uncoordinated swimming movements. They suffer from shortness of breath and bleeding under the skin, which causes dark discoloration. The abdomen is bloated, causing the anus to bulge outwards. Long strands of feces can be a sign of infection. The course of the disease can be stopped by raising the temperature. Large temperature fluctuations in the water should be avoided as a precaution.

• Kois of all ages are at risk
• Disease is highly contagious
• rising water temperatures in spring favor the spread of the virus
• no infections at water temperatures above 20 degrees Celsius

Koi plague

This colloquial term describes a disease caused by herpes viruses. These are brought in by infected koi that appear healthy. Not every fish that carries the virus will contract koi disease. The viruses are excreted with urine, faeces, gill and skin mucus and reach other organisms via the water. They settle in the spleen, kidneys and gills, where they multiply. When the disease has broken out, skin changes appear in the foreground. Discoloration of fins and gills and increased mucus production can occur.

• Koi can get sick at any age
• Viruses can remain in the organism for a lifetime
• Symptoms often appear at temperatures above 16 degrees Celsius

gas bubble disease

If the pond is filled with fresh water or exposed to direct sunlight, the gas content in the water can increase significantly. If the gas concentration in the water exceeds the concentration in the air, a diffusion imbalance occurs. An environment that is oversaturated with oxygen often leads to the formation of gas bubbles in the body of koi fish. They can develop under the scales, causing them to stick out from the body. If gas bubbles form behind the eyes, they can be pushed out of the eye sockets. There is a risk of blindness here. When the bubbles form in the heart's blood vessels, circulation breaks down and the fish dies.

Affected koi should be placed directly in neutral water. If this is not possible, the water in the affected pool should be replaced as soon as possible. Excess gas can also be reduced with the help of strong water movements.

• all fish regardless of age are endangered
• The disease can cause different types of damage
• no treatment with drugs possible

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