‘Artworks that can swim’ and ‘live gems in the water’—these are the lavish titles koi carps have garnered. With their elegant patterns and colours, they are a popular choice for fish owners, which make them ultimately one of the most common fish species in parks. However, the mismanagement in the feeding process and improper handling during the fishing process may result in different diseases in koi carps. These are the most common koi carp diseases:
1. Ich
Photo Credit: Medium
It is also known as the white spot disease. Ich is a protozoan that starts its life in the pond or koi fish aquarium. However, as it continues to mature, it would eventually attach itself to the koi carp’s skin, gills, or fins. It would burrow underneath the epidermis of the fish. At first, it would appear like small grains of salt on the koi carp’s skin and later on would turn into small white bumps.
Once an ich outbreak in koi carps arises, it can swiftly spread through the group of Koi fish. Furthermore, it can infect every fish existing within the body of water. This disease should be taken seriously because if left untreated, the ich can kill multitudes of fishes in a short span of time. Small koi carps are more likely to succumb to the infection and die first.
Causes
- Koi carp population has a high density
- Poor water quality
- Koi carp is under stress or has low immune activity
- The epidermis of the fish has prior trauma or wound
- Improper quarantine procedures when importing new fishes
Symptoms
- Flashing or rubbing their sides on pond objects
- Lack of colour and dull appearance
- Swimming away from the group
- Lethargy
- Loss of appetite
- White spots
Treatment
- Raise the salt concentration of the tank or the pond to about 0.5 per cent over a period of days.
- Soak the koi carp’s body with 0.2 to 0.4 ppm of malachite green.
- Create a mixture of 400 ppm to 500 ppm of salt and 400 ppm to 500 ppm of sodium hydrogen carbonate and then apply it to the infected koi carp’s body.
- Gradually increase the water temperature to mid-80s Fahrenheit whilst raising aeration. This is the crucial stage of the treatment since the root of this disease is the lack of warm temperature.
2. Aeromonas Hydrophila
Photo Credit: Koi Depot in San Diego
‘Motile aeromonas septicemia’ (MAS), ‘haemorrhagic septicemia,’ ‘ulcer disease,’ or ‘red-sore disease’ are the other names for this disease. It is characterised by the lacerations or abrasions caused by the bacterium. It also includes septicaemia, also known as blood poisoning, where the bacterial toxins exist inside various koi fish’s organs and skin ulcers on fish. Aeromonas hydrophila is commonly sequestered from water fish ponds. It is a normal inhabitant within the gastrointestinal tract.
Causes
- Stress
- Low level of nutrition
- Poor quality of water
- A decrease in water temperature
Symptoms
- Pale gills
- Swimming abnormalities
- Bloated appearance
- Skin ulcerations, redness on koi fish’s skin tissue
- Lack of appetite
Treatment
- Administer medicated feed with a total dosage of 2.5–3.75 g of Terramycin, with a generic name of oxytetracycline, per 100 pounds of fish per day for ten days.
- Apply 50 mg of Remet-30, with a generic name of norfloxacin, per kilogram of fish per day for five days.
However, it is encouraged that prevention is better than treatment. Therefore, koi carp owner is advised to minimise stress on the koi carp, which includes handling, nutrition, transportation, stocking levels, and water quality. Additionally, it is also crucial to observe proper koi fish care sanitation and filtration procedures.
3. Dropsy
Photo Credit: extension
Koi dropsy disease is also known as bloater or pine cone disease, which reflects the symptoms exhibited by the Koi Carp. It is primarily harmful to individual koi carps rather than a whole collection and usually occurs during late winter and early spring. If left untreated, it may have irreversible effects on the fish and may cause death. It may result in kidney enlargement, which can lead to kidney failure.
Causes
- A bacterial infection that has entered through the fish’s bloodstream and eventually gained access inside the kidney or liver.
- Mitraspora cyprini, a rare fish parasite that attacks the kidney.
Symptoms
- Scales resembling a pine cone
- Thick bloated and fluctuated belly
- Bulging or popping eyes
- Loss of ability to maintain water balance
- Isolation
Treatment
- Prepare a dip bath laced with 5 ppm potassium permanganate and soak the infected fish for two minutes.
- Use 0.5 per cent of saltwater for feeding.
- Another bloated koi cure is by dipping the fish into erythromycin 2.0ppm to 2.5ppm for thirty minutes to fifty minutes.
4. Pox Disease
Photo Credit: Koiphen
This disease is also dubbed as fish pox or carp pox. After being discovered in 1563, it is currently regarded as the oldest fish disease. It is caused by a herpesvirus infection that weakens the koi carp with lesions. Thus, the disease leaves them susceptible to secondary infections caused by other hazardous microorganisms.
The common carp and agasi carp, where the koi carp is clustered into, are considered as the primary hosts. Pox disease has been sighted in most European countries, USA, Japan, Israel, Russia, Malaysia, and Korea. It is usually contracted in freshwater and in some cases, marine and brackish water. It commonly occurs from late autumn to early winter or spring and if the water temperature is below 15 °C.
Causes
The herpesvirus-1 or HPV-1 is the main causative agent of the pox disease.
Symptoms
- Milky white to grey tumours are situated on the various body surfaces of the infected koi carp
- Affected areas have dark pigmentation
- Bulging eye
- Swollen abdomen
- Slight lesions on the fish’s body surface
Treatment
- Inject each afflicted koi carp with 25 mg of chloramphenicol.
- Use a medicated bath which contains 0.2 ppm of chloramphenicol.
- Raise the water temperature and lower the stocking density.
5. Rot Disease
Photo Credit: Koiphen
It is a fish rotting disease that is caused by a fibromyxic bacterium. It causes swift infection and long-standing disease. Rot disease is difficult to contain once it is diagnosed. There are two types of fish rot disease: bacterial rot disease and parasitic rot disease.
It happens during temperatures going beyond 15°C. It starts in April and usually ends in October in the south. Meanwhile, in the north, it begins in May and ends in September. July and August are observed to be the peak months of this disease.
Causes
- Bacterial infection
- Fungus, mites, and insects such as cockroaches
- Rickets caused by parasites like protozoa or myxospores
- Rickets caused by Chinese sturgeon or ringworm
Symptoms
- Shortness of breath
- Koi carp swims slowly
- Body and head will have a black colour
- Koi scales falling off and rotting
Treatment
- Soak the infected fish into 1.5ppm to 2ppm of yellow powder or 0.3ppm of erythromycin.
- Regular water cleaning and disinfection is in order to reduce the chances of pathogens.
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Important Reminders
Daily inspection of the koi carp’s habitat and the condition is important to effectively avoid these common diseases. Remember to check the water’s temperature especially during extra hot and cold days to know if you need to make adjustments. If the koi carps do exhibit symptoms of these diseases, immediately apply the necessary treatments to avoid dire consequences.
