Koi Diseases and Treatments

Koi Diseases by Symptoms Table

Sort through all 54 diseases that could be harming your koi. Use the search feature to look for keywords, change the amount of results that are being shown, and use pagination to select a different page.

Original Source: ZNA (Zen Nippon Airinkai) Magazine. Translated with permission by Kodama Koi Farm

Symptoms	Disease	Category
White cloud like opaque mucus on the body surface.	White Could disease, Chilodonella, Ichthyobodo, White Spot disease, Trichodina, Gyrodactylus, Dactylogyrus.	Body/External
The body surface is opaque and cloudy.	Chilodonella, White Spot disease, Cold.	Body/External
Abnormal secretion of mucus.	Gyrodactylus, Dactylogyrus, Columnaris disease, Bacterial White Cloud disease.	Body/External
Loss of mucus/slime coat (on skin), skin feels like “sandpaper”.	Chilodonella, Gyrodactylus, Dactylogyrus	Body/External
Numerous white spots.	White Spot disease	Body/External
Red congestion or bleeding.	Chilodonella, Ichthyobodo, Trichodina, Gyrodactylus, Dactylogyrus, Argulosis, Epistyliasis, Dropsy (Pinecone disease), White Spot disease, White Cloud disease, Edema disease.	Body/External
“Worm-hole” like appearance of scales with white spots on the skin.	Epistyliasis	Body/External
Red congestion on the fins. Fins become split, like a broom.	Columnaris disease	Body/External
The scales are coming off. Skin loses slime coat/mucus, may become/appear white.	Columnaris disease	Body/External
Mold or fungus stuck to the body.	Fungal infection, Hole disease.	Body/External
Scales rise up/protruding in a particular area or entire body, like a pine cone.	Pinecone disease, Hole disease, Epistyliasis, White Cloud disease.	Body/External
Holes on the scales/skin.	Hole disease	Body/External
Holes on the scales/skin as well as other parts of the body.	New hole disease	Body/External
Red congestion, red spots, and/or ulcers on the body.	Red disease or Motile Aeromonas, New hole disease, Hole disease.	Body/External
Swollen abdomen.	Pinecone disease, Intestinal Thelohanellosis, Cold.	Body/External
White or pale pink tumors.	Papilloma	Body/External
Protuberant tumors only in the red/scarlet parts of skin.	Hikui disease (red color/pattern rot disease)	Body/External
Translucent, rod-like parasite that is approx. 0.2 inches (5mm) to 0.4 inches (10mm) in size.	Anchor Worm (parasite).	Body/External
Translucent, disc-shaped parasite that is approx. 0.2 inches (5mm) in diameter.	Argulosis, Argulus Infestation, or Fish Louse	Body/External
Anus becomes red or bleeding.	Overfeeding, bloating of the abdominal region, poor digestion.	Body/External
Body of juvenile Koi becomes swollen and transparent.	Edema disease.	Body/External
Gathering around the water return/waterfall.	Hole disease, White Spot disease, Gyrodactylus, Dactylogyrus, Chilodonella, Ichthyobodo, Columnaris Disease, Apiosoma, Myxobolus Koi infection,, Dropsy (Pinecone disease), Edema disease.	Swimming & Grouping
Gathering around the water outlet; bottom drain/skimmer.	Chilodonella, Gyrodactylus, Dactylogyrus, White Spot disease, Edema disease.	Swimming & Grouping
Will not come up to be fed.	White Spot disease, White Cloud disease, Argulosis, Hole disease, Pinecone disease, Ichthyobodo, Chilodonella, Dactylogyrus, Gyrodactylus, Columnaris, Myxobolus Koi infection, Intestinal Thelohanellosis, Apiosoma.	Swimming & Grouping
One or several Koi swim separately from the rest of the group. Stays away from other Koi in the corners/bottom of pond.	Gill disease, Argulosis, White Spot disease, Columnaris.	Swimming & Grouping
Koi stays still on the bottom of the pond.	White Spot disease, Trichodina, Chilodonella, Ichthyobodo, Argulosis, Myxobolus Koi infection, Gyrodactylus, Dactylogyrus.	Swimming & Grouping
Koi is laying down at bottom of pond.	Sleeping Disease, Cold.	Swimming & Grouping
Swimming slowly and lethargically.	Chilodonella, Columnaris, Dactylogyrus, Gyrodactylus, Argulosis, Myxobolus Koi Infection, Apiosoma, Edema disease, Dropsy, White Cloud Disease, Cold, Bloating of the abdominal region.	Swimming & Grouping
Floating at or near surface of water.	Argulosis, White Spot disease, Myxobolus Koi infection, Gyrodactylus, Dactylogyrus, Trichodina, Chilodonella, Columnaris, Ichthyobodo, Edema disease, Apiosoma, KHV (Koi Herpes Virus).	Swimming & Grouping
Rubbing against the walls or bottom of pond.	White Spot disease, Argulosis, Anchor Worm, Epistyliasis, Chilodonella, Myxobolus, Gyrodactylus, Ichthyobodo, Columnaris.	Swimming & Grouping
Shaking the dorsal or pelvic fins.	Anchor Worm.	Swimming & Grouping
Swimming/reacting hyper sensitively.	Anchor Worm, Argulosis, White Spot disease, pH shock.	Swimming & Grouping
Jumping out of the water often/repeatedly.	Anchor Worm (parasite).	Swimming & Grouping
Swelling in the pectoral region with sagging abdomen which is partly constricted.	Pectoral swelling, sagging abdomen.	Body/Appearance
Swollen and curved abdomen.	Bloating of the abdominal region.	Body/Appearance
Becoming skinny due to loss of flesh on the dorsal region.	Chilodonella, Bloating of the abdominal region.	Body/Appearance
Bulging eyes or eyes popping out.	Pinecone disease, Bloating of abdominal region.	Body/Appearance
Sunken eyes.	Chilodonella, Bloating of the abdominal region.	Body/Appearance
Rotten and infected eyes.	Hole disease, Columnaris.	Body/Appearance
Deformed or damaged mouth, fins, or gills.	Columnaris	Body/Appearance
Convulsions, or windy/erratic swimming.	Atrophic Loin	Body/Appearance
Becoming white around the gills.	Chilodonella, Gyrodactylus, Dactylogyrus	Gills
The gills become white due to abnormal secretion of mucus.	Gyrodactylus, Dactylogyrus, Ichthyobodo, Chilodonella, Trichodina, Myxobolus	Gills
The base of the gill covers become white.	Columnaris	Gills
The white gills are observed when the gill covers are opened.	Columnaris, Apiosoma	Gills
The center of the gills become gray or yellow and is damaged.	Columnaris	Gills
The white granular spots are observed on the gill tissues.	Myxobolus	Gills
The gill covers remain open.	Myxobolus, Gyrodactylus	Gills
The gills become reddish black.	Myxobolus	Gills
Drastic mass mortality.	Oxygen Deficiency, Columnaris, Red Disease or Molile Aeromonas Disease, KHV, Poisonous Substances	How Koi Died
Several Koi die every day.	Columnaris, White Cloud Disease, Fungus Disease or Saprolegniasis, Parasitic or Bacterial Disease	How Koi Died
No abnormalities were observed until previous day. However, a few Koi suddenly start dying every day.	Columnaris, Gill Rot Disease	How Koi Died
Koi dies after making frantic efforts.	Columnaris	How Koi Died
Koi swims inactively around the pouring water pipe and dies.	Columnaris, Myxobolus	How Koi Died
Koi whose body surface solely and slightly becomes red dies.	Columnaris	How Koi Died
The bigger or fatter Koi starts to die first.	Oxygen Deficiency	How Koi Died

The Symptoms, Treatment & Control of Fish Disease Table

We’ve outlined 12 common diseases and included their symptoms, season, and tips for treatment. Use this table with the koi health checklist and the Koi Diseases by Symptoms Table to identify the source of the health problem of your koi.

Original Source: ZNA (Zen Nippon Airinkai) Magazine. Translated with permission by Kodama Koi Farm

Disease	Symptoms	Season	Treatment & Control
Anchor Worm	The infected sites become colored, congested, and rigid because of abnormal secretion of mucus and proliferation of epidermal cells. The size of rod-shape parasite is 3mm to 12mm, so it is easy to find the parasite sticking to the fish.	Spring to Autumn. 59°F (15°C) or higher water temp.	Removal with tweezers or medications. Trichlorfon 0.2 - 0.5 ppm to kill Anchor worm’s larvae. Use it 2 - 3 times every 2 - 3 weeks Demilin 2g/t (53.6°F (12°C)) or higher water temp.
Argulosis (Fish Lice)	Infected Koi wiggles their pectoral fins and shakes their dorsal fins. Also, Koi displays violent erratic swimming and scrapes itself on the bottom or on the wall of the pond.	Spring to Autumn. 59°F (15°C) or higher water temp.	Removal with tweezers or medications. Trichlorfon 0.2 - 0.5 ppm to kill Anchor worm’s larvae. Use it 2 - 3 times every 2 - 3 weeks
White Spot Disease	Tiny white spots are observed first on the head or pectoral fins, and the infected sites are extended to whole body. The infected Koi often scrapes the body sides to the bottom of the pond, loses appetite, gathers near the water inlet, hangs beneath the water surface, or moves less and less on the bottom of the pond.	6°C (43°F) to 25°C (77°F) of the water temp.	Bath treatment with: 1) 5kg (11lb) of salt / t (264 gallons) for five to seven days 2) 10kg(22lb) of salt / t (264 gallons) for one hour in a day for three days. 3) 2 g of Methylene blue / t (264 gallons) for three days 4) 0.1 to 0.2 g of Malachite green for three days. 5) 20 to 25 cc of Formalin / t (264 gallons) 6) Warm the water temp. up more than 28°C (82°F) so that the life cycle of the parasites stops naturally.
Ichthyobodosis (Costiosis)	The infection causes the white cloud like opaque mucus and erosion on the body surface. The infected Koi loses the appetite, gathers near the water inlet, hangs beneath the water surface, moves less and less on the bottom of the pond. Once gills get infected, Koi can not breath and die.	November to April	1- 20 to 25cc of formalin / t (264 gallons) for two to three days. 2 - 2 to 3g of potassium permanganate / t (264 gallons). 3- 5g of potassium permanganate / t (264 gallons) for one hour in a day at every two days for three times. 4 - 200g (7oz)of potassium permanganate/ t (264 gallons) for five minutes. ※ 3 and 4 are only performed to Koi of three years or older. Do not exceed the time of bath treatment. Stop the bath treatment if any abnormalities are observed such as swimming with their nose up on the water surface. 5 - 6 to 7kg (13 to 15.5LB) of salt / t (264 gallons ) for five to seven days. 6 - 10 ml of Pro Form-C / 100 gal. three times daily with 25% water change.
Chilodonellosis	The infection can be observed on gills and the body surface as well as fins. The infection causes the white cloud like opaque mucus on the body surface. The infected Koi loses appetite and weight, hangs beneath the water surface, and moves less. When gills are infected, the Koi gathers around the water inlet due to breathing difficulty. In severe case, the skin becomes like a sandpaper. Also, the congestion is observed on the skin.	Under 20°C (68°F) of the water temp. Especially between 10°C (50°F) and 15°C (59°F) of the water temp.	Be alert not to get the infection after Koi Show or Koi Hunt. Pay attention when the water temperature is low. The treatment and control for Chilodonellosis are same as Ichthyobososis. See the section of treatment and control for Ichthyobososis.
Trichodinosis (Cyclochita)	The infected surface body becomes thicker due to the excessive mucus secretion. The infected Koi becomes anorexic and floats close to the water surface. Koi gathers around the pouring pipe because of breathing problem when gills are infected. Be extra care not to get infected on the fry because the infection leads to death easily.	All seasons, especially from autumn to winter.	Treatment and control for Chilodonellosis are same as Ichthyobososis. See the section of treatment and control for Ichthyobososis.
Dactylogyrosis, Gyrodactylosis (Fluke)	The gills are mainly parasitized and become white due to the excessive mucus secretion. The infected Koi becomes anorexic, floats close to the water surface, and moves less and less. When the fins and the body surface get parasitized, the skin becomes bloodshot as well as white cloud due to excessive mucus secretion.	All seasons.	1 - 20 to 25cc of formalin / t (264 gal.) for three to five days. 2 - 3g of potassium permanganate / t (264 gal.) for two hours. 3 - 5g of potassium permanganate/ t (264 gal.) for one hour. 4 - 200g (7oz) of potassium permanganate / t (264 gal.)for five minutes. ※ 2, 3, and 4 are only performed to Koi of three years or older. Do not exceed the time of the bath treatment. Stop the bath treatment if any abnormalities are observed such as swimming with their nose-up on the water surface.
Columnaris (gill rot, mouth rot, fin rot, and dermal rot disease)	The infected Koi loses appetite, gathers near the water inlet, hangs beneath the water surface or moves less and less. The disease causes the mortality of the Koi due to the emaciation. White and yellow substances are observed on the whole body. The body covers with cloudy mucus gradually. Scales and mucus come off consequently, and it makes the fish appear as if covered in white rags.	20°C (68°F) of the water temp. or higher.	The disease must be found at early stage like when only one of the gill is closed. 1 - 6 to 7kg (13 to 15.5LB) of the salt /t (264 gal. ) for five to seven days. 2 - Oxytetracycline with salt5 -6 kg /t (264 gal.) for 10 days 3 - Oxolinic Acid with salt 5 -6 kg /t (264 gal.) for 10 days
Pine cone disease	Scales of infected Koi raise up, and heavily infected Koi resembles a "pine cone". In most case, the skin is bleeding. Swollen abdomen and pop-out eyes are also observed. Infectivity is weak when scales raise up on the whole body. However, when scales raise up partly and spread on the whole body gradually, the infectivity tends to be strong. Aeromonas hydrophila causes this disease. Overeating starch and fat could cause the disease, too.	Early spring.	Aeromonas is not very infective. Pay attention to water quality and keep COD under 5ppm 1 - Oxytetracycline with salt 5 kg /t (264 gal.) for 5 to 7 days 2 - Oxolinic Acid with salt 5 -6 kg /t (264 gal.) for 5 to 7 days. 3 - For big Koi, the surgical knife is inserted under the raised scales, and the pus is drawn out carefully by pressing. After the iodine tincture is applied on the wound, bath treatment of 1 or 2 mentioned above is performed. 4 - Mix 0.1g of Oxolinic acid with food per koi weight 1 kg (2.2lb) and feed for 5 to 7 days.
Hole Disease	The muscle is exposed on the body surface as if the muscle is carved out by the spoon. The ulcer will be found in the abdomen, dorsal or tail section. They look like the hole is made. The section where anchor worms or fish louses are stuck mainly infects first. The affected section spreads gradually. The hole disease is developed in the section where the disease signs are hard to find such as the mouth, the base or tip of fins, and the abdomen. Even just a single Koi gets the hole disease, the treatment is needed to all fish in the pond because the disease is contagious.	April to June. Oct. to Nov.	The incidence of the hole disease will be higher with the water quality becomes worse. Maintain COD lower than 5PPM. 1 - Oxytetracycline with salt 5 kg /t (264 gal.) for 10 days 2 - Oxolinic Acid with salt 5 -6 kg /t (264 gal.) for 10 days.3 - Mix 0.1g of Oxolinic acid with food per koi weight 1 kg (2.2lb) and feed for 5 to 7 days.4 - Use Dryer to blow out the affected area for ten seconds. Repeat three times and put the medicine on the affected area. The treatment is performed for three days in a row. Be careful not to blow warm air into eyes or gills.5 - Add aerobic bacteria
New Hole Disease	Despite the absence of infections such as the anchor worm, roughly a single scale becomes red or bloodshot, the top of the fins hemorrhage and break-down during the early stage of this disease. In its progressed stage, the congestion proliferates. Moreover, the diseased fish display ulcers, drop-out of scale and loss of each fin, which are known as the typical symptoms of the hole disease. However, the difference from the traditional hole disease is that antibacterial medicine do not work. Moreover, the symptoms appear not only in the mouth, throat, gill covers, head, and face, but also in the section, where it is hard to find by looking down on the pond, such as the base of fins and the lower jaw.	All seasons especially when the season changes.	The new hole disease is caused by non-typical Aeromonas salmonicida which is the resistant to the anti-bacterial medicine for aquatic organisms such as oxolinic acid and HCL-oxytetracyclin. Because the progression of this disease is faster and mortality rate is higher than the hole disease, it is very important to detect and treat the new hole disease in its early stage. 1 - Adsorb 0.05 to 0.1mL of 10%Enrofloxacin liquid per day per 1kg (2.2LB) of fishweight to 80 - 50% of pellet food of thequantity usually fed. Feed for 5 to 7 days. 2 - Adsorb 0.02g of 25% Difloxacin solublepowder per day per 1kg (2.2LB) of fish weight to80 - 50% of pellet food of the quantityusually fed. Feed for 5 to 7 days. 3 - Adsorb 0.5mL of 2% Florfenicol foraquatic organisms per day per 1kg (2.2LB) of fishweight to 80 - 50% of fish food usually fed.Feed for 5 days. 4 - 0.2 - 0.4mL of 2.5% Enrofloxacin injection or 0.1 - 0.2mL of 5% Enrofloxacin injection per 1kg (2.2LB) of fish weight at a time. Injection should be made once per day for 3 - 5 days. 1 - Application of an ointment: The disinfectant for juman external wounds such as Iodine Tincture,Povidoneiodine are good to use to disinfect the diseased hole part in seriously diseased fish. This should be done along with oral administration or injection 2 - Dryer treatment: blow out the affected area for ten seconds. Repeat three times and put the medicine on the affected area. The treatment is performed for three days in a row. Be careful not to blow warm air into eyes or gills. 3 - Scatter the aerobic bacteria such as Niigata Water Bio.