Koi Fish Health Conditions

Browse 166 guides from veterinary sources about koi fish health conditions.

Acquired Skeletal Deformities in Koi Fish

Learn the causes, symptoms, diagnosis, prevention, and treatment options for acquired skeletal deformities in koi fish,...

Aeromonas Ulcer Disease in Koi Fish: Red Sores, Septicemia, and Care

See your vet immediately if your koi has red sores or ulcers. Learn Aeromonas signs, causes, diagnosis, treatment...

Age-Related Spinal Degeneration in Koi Fish: Osteophytes, Stiffness, and Weak Swimming

Learn how aging-related spinal changes affect koi, including stiffness, weak swimming, diagnosis, care options, and...

Age-Related Tumors in Koi Fish: Why Older Koi Develop More Masses

Older koi can develop benign or cancerous masses with age. Learn signs, diagnosis, pond care, and treatment options...

Ammonia Poisoning in Koi Fish: Emergency Signs, Causes, and What to Do

Ammonia poisoning in koi fish can turn critical fast. Learn emergency signs, common causes, diagnosis, treatment...

Ammonia-Related Eye Damage in Koi Fish: Irritation and Cloudy Eyes

Ammonia in pond water can irritate koi eyes and cause cloudiness. Learn symptoms, causes, diagnosis, prevention, and...

Anchor Worm in Koi Fish: Lernaea Parasites, Visible Worms, and Care

Anchor worm in koi causes visible thread-like parasites, red sores, and flashing. Learn symptoms, diagnosis, treatment...

Anchor Worm in Koi Fish: Skin Parasite Removal and Prevention

Anchor worm in koi can cause red sores, flashing, and infection. Learn symptoms, removal options, treatment cost...

Autoimmune and Immune-Mediated Disease in Koi Fish: What Owners Need to Know

Learn how immune-mediated disease may affect koi, what signs to watch for, how your vet diagnoses it, and practical...

Biliary Stasis and Cholestasis in Koi Fish: When Bile Flow Is Impaired

Learn signs, causes, diagnosis, treatment options, and prevention for biliary stasis and cholestasis in koi fish,...

Branchiomycosis in Koi Fish: Gill Rot, Breathing Distress, and Outbreak Risk

Branchiomycosis in koi is a rare but urgent gill fungus that can trigger breathing distress and pond outbreaks. Learn...

Carp Edema Virus in Koi Fish: Sleeping Disease Signs and Treatment Basics

Learn the signs of carp edema virus in koi, how vets diagnose sleeping disease, treatment options, prevention steps,...

Carp Pox in Koi Fish: Waxy White Growths, Causes, and Care

Learn how to recognize carp pox in koi, what causes waxy white growths, when to call your vet, and practical care...

Carp Pox in Koi Fish: Waxy White Skin Growths Explained

Learn what carp pox in koi looks like, what causes waxy white growths, when to see your vet, and how quarantine and...

Cataracts in Koi Fish: Lens Opacity, Vision Changes, and Management

Learn how cataracts affect koi vision, what causes cloudy lenses, when to see your vet, and practical management...

Chemical Toxicity and Poisoning in Koi Fish: Pond Toxins Every Owner Should Know

Learn the warning signs of chemical poisoning in koi, common pond toxins, vet diagnosis, treatment options, prevention...

Chilodonella in Koi Fish: Cloudy Skin and Lethargy Causes

Chilodonella in koi can cause cloudy skin, excess slime, flashing, and lethargy. Learn causes, diagnosis, treatment...

Chilodonella in Koi Fish: Skin and Gill Parasite Signs and Treatment

Chilodonella in koi can cause flashing, excess mucus, and breathing trouble. Learn signs, diagnosis, treatment options,...

Chlorine and Chloramine Poisoning in Koi Fish: Water Change Emergencies

See your vet immediately if koi gasp after a water change. Learn signs of chlorine or chloramine poisoning, emergency...

Chondroma and Chondrosarcoma in Koi Fish: Cartilage Tumors in Fins and Body

Learn signs, diagnosis, treatment options, and realistic cost ranges for chondroma and chondrosarcoma in koi fish with...

Cloacitis and Proctitis in Koi Fish: Inflamed Vent and Lower Digestive Tract

Learn signs, causes, diagnosis, prevention, and treatment options for cloacitis and proctitis in koi fish, including...

Cloudy Eye in Koi Fish: Corneal Opacity Causes and Care

Cloudy eye in koi fish can signal injury, infection, parasites, or water-quality stress. Learn symptoms, diagnosis,...

Cloudy Skin and Excess Mucus in Koi Fish: Common Dermatologic Causes

Cloudy skin and excess mucus in koi often point to parasites, water quality stress, or infection. Learn symptoms,...

Coccidiosis in Koi Fish: Intestinal Protozoal Disease in Carp and Koi

Coccidiosis in koi is an intestinal protozoal disease that can cause weight loss, poor growth, and deaths in young...

Columnaris Disease in Koi Fish: Mouth Rot, Gill Damage, and Fast Treatment

Columnaris in koi can cause mouth rot, skin ulcers, and gill damage fast. Learn symptoms, diagnosis, treatment options,...

Columnaris in Koi Fish: Skin Lesions, Saddleback Changes, and Care

Columnaris in koi can cause skin sores, cottony patches, and saddleback lesions. Learn symptoms, diagnosis, treatment...

Congenital Skeletal Deformities in Koi Fish

Learn signs, causes, diagnosis, prevention, and care options for congenital skeletal deformities in koi fish, with real...

Constipation in Koi Fish: Signs of Digestive Blockage and What to Do

Learn the signs of constipation in koi fish, common causes, when blockage is urgent, treatment options, and how your...

Copper Poisoning in Koi Fish: Medication, Algaecide, and Water Source Dangers

Copper poisoning in koi can cause rapid breathing, gill damage, and sudden death. Learn signs, causes, diagnosis,...

Costia in Koi Fish: Cloudy Skin, Flashing, and Early Warning Signs

Costia in koi can cause cloudy skin, flashing, and fast breathing. Learn early warning signs, diagnosis, prevention,...

Costia in Koi Fish: Ichthyobodo Infection, Skin Slime, and Flashing

Costia in koi can cause flashing, gray-blue slime, breathing trouble, and fast decline. Learn symptoms, diagnosis,...

Degenerative Spinal Disease and Osteophytes in Koi Fish

Learn signs, causes, diagnosis, care options, and prevention for degenerative spinal disease and osteophytes in koi...

Developmental Deformities in Koi Fish: Congenital Body Shape and Growth Problems

Learn how congenital and developmental deformities affect koi body shape, growth, swimming, diagnosis, prevention, and...

Dystocia in Koi Fish: Spawning Problems and Emergency Care

See your vet immediately if a koi is swollen and cannot spawn. Learn signs, causes, diagnosis, prevention, and...

Edwardsiellosis in Koi Fish: Internal Bacterial Infection and Warning Signs

Edwardsiellosis in koi is a serious internal bacterial infection that can cause ulcers, buoyancy changes, and sudden...

Egg Binding and Egg Retention in Koi Fish: Causes of Swollen Female Koi

Swollen female koi may be carrying eggs, but egg retention can turn serious fast. Learn symptoms, causes, diagnosis,...

Enteritis in Koi Fish: Causes, Signs, and Treatment

Learn the causes, signs, diagnosis, treatment options, and prevention tips for enteritis in koi fish, including when to...

Epitheliocystis in Koi Fish: Gill Infection, Breathing Trouble, and Diagnosis

Epitheliocystis in koi can cause gill cysts, fast breathing, and low oxygen stress. Learn symptoms, diagnosis,...

Epizootic Ulcerative Syndrome in Koi Fish: Deep Ulcers and Water Mold Infection

Learn the signs, causes, diagnosis, prevention, and treatment options for epizootic ulcerative syndrome in koi fish,...

Eye and Neural Tumors in Koi Fish: Bulging Eye, Nerve, and Brain-Related Masses

Learn signs, causes, diagnosis, and care options for eye and neural tumors in koi fish, including bulging eye, balance...

Eye Injuries in Koi Fish: Trauma, Cloudiness, and Bulging Eye Emergencies

Koi eye injuries can cause cloudiness, swelling, or bulging eyes. Learn urgent signs, causes, diagnosis, treatment...

Eye Trauma in Koi Fish: Injuries, Scratches, and Eye Swelling

Koi eye trauma can cause cloudiness, swelling, bleeding, or a bulging eye. Learn causes, warning signs, vet care...

Fibroma and Fibrosarcoma in Koi Fish: Benign vs Malignant Connective Tissue Masses

Learn how fibroma and fibrosarcoma affect koi, what lumps mean, when to see your vet, diagnosis steps, treatment...

Fin Deformities in Koi Fish: Congenital and Inherited Fin Abnormalities

Learn how congenital fin deformities affect koi, what signs to watch for, how your vet evaluates them, and practical...

Fish Lice (Argulus) in Koi Fish: Signs, Skin Damage, and Treatment

Fish lice in koi can cause flashing, ulcers, and stress fast. Learn Argulus signs, skin damage, treatment options,...

Fish Lice in Koi Fish: Argulus Parasites, Scratching, and Pond Treatment

Fish lice in koi can cause scratching, ulcers, and stress. Learn Argulus signs, diagnosis, pond treatment options,...

Furunculosis in Koi Fish: Aeromonas salmonicida Infection and Ulcer Risks

Furunculosis in koi can cause deep ulcers, bleeding, and sudden losses. Learn symptoms, diagnosis, treatment options,...

Gas Bubble Disease in Koi Fish Eyes: Corneal Bubbles and Eye Damage

Gas bubble disease in koi can cause corneal bubbles, popeye, and eye damage. Learn signs, causes, diagnosis,...

Gas Bubble Trauma in Koi Fish: Oxygen Supersaturation and Equipment-Related Injury

Gas bubble trauma in koi is an emergency caused by supersaturated water or equipment leaks. Learn signs, diagnosis,...

Gastroenteritis in Koi Fish: Vomit-Like Regurgitation, Diarrhea, and Gut Upset

Koi gastroenteritis can cause regurgitation, stringy stool, bloating, and lethargy. Learn causes, warning signs, vet...

Gill Flukes in Koi Fish: Dactylogyrus Infection, Breathing Signs, and Treatment

Gill flukes in koi can cause fast breathing, flashing, and pale gills. Learn signs, diagnosis, treatment options,...

Gonadal Tumors in Koi Fish: Causes of Swollen Abdomen and Reproductive Masses

Koi with a swollen belly may have gonadal tumors. Learn symptoms, diagnosis, treatment options, prevention, and...

Heavy Metal Toxicity in Koi Fish: Copper, Zinc, and Other Pond Contaminants

Heavy metal toxicity in koi can cause sudden deaths, lethargy, and gill damage. Learn signs, causes, diagnosis,...

Helminth Infections in Koi Fish: Intestinal Worms, Weight Loss, and Poor Growth

Learn how intestinal worms affect koi, causing weight loss and poor growth, plus symptoms, diagnosis, treatment...

Hemangioma and Hemangiosarcoma in Koi Fish: Blood Vessel Tumors and Bleeding Masses

Learn how blood vessel tumors in koi are recognized, diagnosed, and managed, including bleeding mass warning signs,...

Hepatic Amyloidosis in Koi Fish: Protein Deposits in the Liver

Learn signs, causes, diagnosis, prevention, and treatment options for hepatic amyloidosis in koi fish, including...

Hepatic Lipidosis in Koi Fish: Fatty Liver Disease From Diet and Husbandry Problems

Learn signs, causes, diagnosis, prevention, and treatment options for hepatic lipidosis in koi fish, including diet and...

Hepatic Necrosis in Koi Fish: Severe Liver Tissue Damage and Sudden Illness

Hepatic necrosis in koi is severe liver cell death linked to toxins, infection, or poor water quality. Learn signs,...

Hepatitis in Koi Fish: Liver Inflammation, Causes, and Veterinary Care

Learn signs, causes, diagnosis, treatment options, and prevention for hepatitis in koi fish, including when to contact...

Hepatocellular Carcinoma in Koi Fish: A Rare but Serious Liver Cancer

Learn signs, diagnosis, treatment options, and prevention tips for hepatocellular carcinoma in koi fish, a rare but...

Hereditary Vertebral Deformity in Koi Fish: Genetic Causes of Back and Tail Abnormalities

Learn how hereditary vertebral deformity affects koi fish, what curved backs and tails can mean, how your vet diagnoses...

Hindquarter Paresis in Koi Fish

Hindquarter paresis in koi causes rear-end weakness, sinking, and poor swimming. Learn signs, causes, diagnosis,...

Household Cleaner Poisoning in Koi Fish: Soap, Disinfectant, and Spill Exposure

See your vet immediately if soap, bleach, or disinfectant gets into your koi pond. Learn symptoms, diagnosis, treatment...

Hydrogen Sulfide Poisoning in Koi Fish: Toxic Pond Gas from Sludge and Dead Zones

Hydrogen sulfide poisoning in koi can cause sudden deaths after sludge is disturbed. Learn symptoms, causes, diagnosis,...

Ich (White Spot Disease) in Koi Fish: Symptoms and Treatment

Ich in koi causes white spots, flashing, and breathing trouble. Learn symptoms, diagnosis, treatment options,...

Ich in Koi Fish: White Spot Disease Symptoms, Treatment, and Pond Control

Ich in koi causes white spots, flashing, and breathing trouble. Learn symptoms, treatment options, pond control,...

Ileus in Koi Fish: Reduced Gut Motility and Digestive Stasis

Learn the signs, causes, diagnosis, prevention, and treatment options for ileus in koi fish, including when reduced gut...

Inbreeding Problems in Koi Fish: Genetic Risks, Deformities, and Reduced Vigor

Learn how inbreeding can affect koi with deformities, weak growth, and lower disease resistance, plus diagnosis,...

Intestinal Obstruction in Koi Fish: When a Digestive Blockage Becomes an Emergency

Intestinal obstruction in koi fish can turn critical fast. Learn warning signs, causes, diagnosis, treatment options,...

Intestinal Parasites in Koi Fish: Worms and Protozoa That Affect Digestion

Intestinal parasites in koi can cause weight loss, poor appetite, and stringy stool. Learn signs, diagnosis, treatment...

Iodine Deficiency and Goiter in Koi Fish: Thyroid Enlargement Explained

Learn how iodine deficiency can cause goiter in koi fish, what throat swelling means, when to see your vet, and...

Jaw and Mouth Deformities in Koi Fish: Congenital Feeding Problems Explained

Learn how congenital jaw and mouth deformities affect koi feeding, growth, and care, plus symptoms, diagnosis,...

Koi Fish Ammonia Gill Burn: Chemical Gill Damage and Gasping

Koi ammonia gill burn can cause gasping, red or damaged gills, and sudden decline. Learn symptoms, causes, diagnosis,...

Koi Fish Bacterial Gill Disease: Swollen Gills and Trouble Breathing

Koi with swollen gills or gasping may have bacterial gill disease. Learn symptoms, causes, diagnosis, treatment...

Koi Fish Blood Flukes: Gill Vessel Damage and Respiratory Stress

Koi blood flukes can injure gill vessels and trigger breathing distress. Learn signs, diagnosis, treatment options,...

Koi Fish Cardiac Edema: Heart-Related Fluid Retention and Swelling

Koi fish cardiac edema causes swelling, bloating, and weakness. Learn symptoms, diagnosis, treatment options,...

Koi Fish Cardiomyopathy: Heart Muscle Disease in Koi

Learn signs, causes, diagnosis, treatment options, and prevention for cardiomyopathy in koi, plus when your vet should...

Koi Fish Carp Edema Virus (CEV): Koi Sleepy Disease and Gill Infection

Carp edema virus in koi can cause severe lethargy, gill damage, and sudden losses. Learn symptoms, diagnosis, treatment...

Koi Fish Congenital Heart Defects: Cardiac Malformations in Koi

Learn signs, diagnosis, care options, and realistic vet cost ranges for congenital heart defects and cardiac...

Koi Fish Congestive Heart Failure: Fluid Retention and Poor Circulation in Koi

Koi congestive heart failure can cause swelling, lethargy, and breathing trouble. Learn signs, causes, diagnosis,...

Koi Fish Gill Flukes: Causes of Rapid Breathing and Gill Irritation

Koi gill flukes can cause rapid breathing, flashing, and pale swollen gills. Learn causes, diagnosis, prevention, and...

Koi Fish Gill Hyperplasia: Overgrown Gill Tissue and Breathing Difficulty

Koi gill hyperplasia can cause gasping, lethargy, and low oxygen stress. Learn causes, diagnosis, treatment options,...

Koi Fish Gill Rot: Necrotic Gill Disease in Koi

Koi gill rot can cause fast breathing, pale or damaged gills, and sudden losses. Learn causes, diagnosis, treatment...

Koi Fish Hypoxia: Low Oxygen Stress, Gasping, and Surface Breathing

Koi fish hypoxia can cause gasping, surface breathing, and sudden losses. Learn signs, causes, diagnosis, treatment...

Koi Fish Kidney Disease from Koi Herpesvirus: Renal Involvement in KHV

Koi herpesvirus can damage the kidneys and gills, causing sudden illness and death in koi. Learn signs, diagnosis,...

Koi Fish Kidney Tumors: Renal Neoplasia in Koi

Learn signs, diagnosis, treatment options, and realistic 2026 US cost ranges for kidney tumors in koi, including when...

Koi Fish Koi Herpesvirus (KHV): Gill Disease, Breathing Problems, and Sudden Death

Koi herpesvirus can cause severe gill damage, breathing trouble, and sudden death in koi. Learn signs, diagnosis,...

Koi Fish Neoplasia and Tumors: Types, Signs, and Treatment

Learn how tumors affect koi, common warning signs, diagnosis, treatment options, and realistic veterinary cost ranges...

Koi Fish Nephritis: Kidney Inflammation, Swelling, and Systemic Illness

Learn signs, causes, diagnosis, prevention, and treatment options for koi fish nephritis, including swelling, dropsy,...

Koi Fish Nephroblastoma: A Kidney Tumor That Can Cause Abdominal Swelling

Koi nephroblastoma is a kidney tumor that can cause abdominal swelling, poor buoyancy, and appetite loss. Learn signs,...

Koi Fish Nephrocalcinosis: Mineral Deposits and Chronic Kidney Damage

Learn how nephrocalcinosis affects koi, what signs to watch for, how your vet diagnoses it, and pond steps that may...

Koi Fish Nephrosis and Kidney Failure: Signs of Renal Damage in Koi

Koi kidney failure can cause swelling, lethargy, and sudden death. Learn signs, causes, diagnosis, prevention, and...

Koi Fish Nitrite Poisoning (Brown Blood Disease): Oxygen Transport Failure

See your vet immediately if koi are gasping or hanging at the surface. Learn signs, causes, diagnosis, prevention, and...

Koi Fish Renal Dropsy: Fluid Retention Linked to Kidney Disease

Koi renal dropsy causes swelling, raised scales, and lethargy from kidney damage. Learn symptoms, diagnosis, treatment...

Koi Fish Saprolegnia Gill Infection: Fungal Gill Disease in Koi

Koi gill fungus can cause fast breathing, pale gills, and sudden decline. Learn signs, diagnosis, treatment options,...

Koi Fish Spring Viremia Kidney Damage: Renal Signs of SVC

Learn how spring viremia of carp can affect koi kidneys, what renal signs to watch for, how vets diagnose SVC, and...

Koi Fish Spring Viremia of Carp: Systemic Viral Disease Affecting Gills and Kidney

Spring viremia of carp is a reportable viral disease in koi. Learn symptoms, diagnosis, prevention, and realistic...

Koi Fish Ulcer Disease: Causes, Signs, and Treatment

Learn what causes koi ulcer disease, early warning signs, diagnosis, treatment options, and prevention steps to protect...

Koi Herpesvirus Disease in Koi Fish: Symptoms, Spread, and What to Do

Koi herpesvirus disease can spread fast and cause high losses in koi. Learn the signs, how it spreads, diagnosis steps,...

Koi Herpesvirus in Koi Fish: Skin Changes, Mucus Loss, and Warning Signs

Koi herpesvirus can cause mucus loss, rough skin, gill damage, and sudden deaths in koi. Learn warning signs,...

Lipoma and Liposarcoma in Koi Fish: Fatty Tumors and Cancer Concerns

Learn how lipomas and liposarcomas affect koi, what lumps may mean, when to see your vet, diagnosis options, and...

Liver Disease in Koi Fish: General Hepatopathy Signs and Causes

Learn the signs, causes, diagnosis, and prevention of liver disease in koi fish, including water-quality risks, toxins,...

Liver Failure in Koi Fish: Advanced Hepatic Disease and Emergency Warning Signs

Learn the emergency signs of liver failure in koi fish, common causes, diagnosis, treatment options, and prevention...

Liver Tumors in Koi Fish: Hepatic Neoplasia, Masses, and Prognosis

Learn signs, diagnosis, treatment options, cost ranges, and prognosis for liver tumors in koi fish, including when to...

Localized Scale Protrusion in Koi Fish: Skin Infection Under the Scales

Localized raised scales in koi can signal an ulcer or bacterial skin infection. Learn symptoms, causes, diagnosis,...

Loss of Appetite in Koi Fish: Digestive Causes to Consider

Koi not eating? Learn digestive causes, warning signs, diagnosis, prevention, and realistic vet cost ranges for...

Lymphocystis in Koi Fish: White to Pink Skin Nodules Explained

Learn what white to pink nodules on koi may mean, how lymphocystis is diagnosed, when to call your vet, treatment...

Lymphoma and Lymphosarcoma in Koi Fish: Internal Cancer Signs and Diagnosis

Learn the internal signs of lymphoma and lymphosarcoma in koi fish, how your vet diagnoses it, and realistic 2026 US...

Malabsorption in Koi Fish: When Nutrients Are Not Properly Absorbed

Learn the signs, causes, diagnosis, and care options for malabsorption in koi fish, including parasites, diet issues,...

Medication Overdose in Koi Fish: Treatment Toxicity from Common Pond Products

Koi medication overdose can cause gasping, rolling, and sudden death. Learn common pond product risks, emergency steps,...

Melanoma and Pigmented Tumors in Koi Fish: Dark Masses Explained

Learn what dark masses in koi may mean, how vets diagnose pigmented tumors, when to worry, and realistic 2026 U.S. care...

Mouth Rot in Koi Fish: Oral Infection, Erosion, and When to Seek Help

Koi mouth rot can cause ulcers, erosion, and trouble eating. Learn signs, causes, vet diagnosis, prevention, and...

Muscle Disorders in Koi Fish

Learn signs, causes, diagnosis, prevention, and treatment options for muscle disorders in koi fish, including weakness,...

Mycobacteriosis in Koi Fish: Chronic Wasting Disease and Zoonotic Concerns

Learn the signs, diagnosis, prevention, and zoonotic risks of mycobacteriosis in koi fish, plus realistic veterinary...

Myelomalacia in Koi Fish

Myelomalacia in koi is a severe spinal cord injury or softening that can cause paralysis. Learn signs, diagnosis, care...

Myxozoan Intestinal Disease in Koi Fish: Gut Parasites That Cause Emaciation

Myxozoan intestinal disease in koi can cause weight loss, poor growth, and death. Learn symptoms, diagnosis,...

Netting and Handling Injuries in Koi Fish: Preventing Scale Loss and Soft Tissue Damage

Learn how netting and handling injure koi, what signs to watch for, when to see your vet, and how to protect scales,...

Neurologic Disorders in Koi Fish

Neurologic disorders in koi can cause circling, loss of balance, and sinking or floating. Learn causes, diagnosis,...

Nitrate Toxicity in Koi Fish: Chronic Water Quality Poisoning Explained

Learn how chronic nitrate buildup affects koi, common symptoms, diagnosis, treatment options, prevention steps, and...

Nitrite Poisoning in Koi Fish: Brown Blood Disease and Pond Safety

Nitrite poisoning in koi can turn deadly fast. Learn symptoms, causes, diagnosis, treatment options, and pond safety...

Noninfectious Egg-Associated Coelomic Swelling in Koi Fish

Learn signs, causes, diagnosis, prevention, and treatment options for noninfectious egg-associated coelomic swelling in...

Oral Abscess in Koi Fish: Pus-Filled Mouth Infections and Feeding Problems

Koi oral abscesses can cause mouth swelling, pus, and feeding trouble. Learn symptoms, causes, vet diagnosis, treatment...

Oral Trauma in Koi Fish: Mouth Injuries From Netting, Spawning, or Pond Hazards

Koi mouth injuries from nets, spawning, or pond hazards can lead to pain, infection, and poor feeding. Learn signs, vet...

Oral Tumors in Koi Fish: Mouth Growths, Masses, and Next Steps

Learn what mouth growths in koi may mean, when to see your vet, diagnosis options, treatment paths, and realistic 2026...

Oral Ulcers in Koi Fish: Mouth Sores, Causes, and Recovery

Koi mouth sores can signal infection, trauma, or poor water quality. Learn symptoms, diagnosis, treatment options,...

Oropharyngeal Foreign Body in Koi Fish: Objects Stuck in the Mouth or Throat

Koi with something stuck in the mouth or throat need urgent veterinary care. Learn signs, diagnosis, treatment options,...

Osteoma and Osteosarcoma in Koi Fish: Bone Tumors and Facial Deformity

Learn signs, diagnosis, treatment options, and cost range for osteoma and osteosarcoma in koi fish, including facial...

Papilloma in Koi Fish: Wart-Like Growths and Cancer Risk

Papilloma in koi fish causes smooth, waxy wart-like growths, often from carp pox. Learn symptoms, diagnosis,...

Papillomas in Koi Fish: Warty Skin Growths and When to Worry

Learn what warty skin growths in koi may mean, when papillomas are harmless, and when your vet should check for...

Paralysis in Koi Fish: Neurologic and Spinal Causes

Paralysis in koi fish is an emergency. Learn common neurologic and spinal causes, warning signs, diagnosis, prevention,...

Pesticide and Herbicide Poisoning in Koi Fish: Yard Chemical Risks for Pond Fish

See your vet immediately if koi act distressed after lawn treatment. Learn signs, diagnosis, prevention, and realistic...

Pharyngeal Mass in Koi Fish: Growths and Abscesses Near the Throat

Learn signs, causes, diagnosis, treatment options, and cost range for pharyngeal masses in koi, including throat...

Pharyngeal Teeth Injury in Koi Fish: Hidden Oral Damage That Affects Eating

Koi with pharyngeal teeth injury may chew poorly, spit food, or stop eating. Learn signs, causes, diagnosis,...

Pharyngeal Teeth Malocclusion in Koi Fish: Dental Misalignment and Feeding Trouble

Learn signs, causes, diagnosis, and care options for pharyngeal teeth malocclusion in koi fish, including feeding...

Pharyngitis in Koi Fish: Inflammation of the Throat and Swallowing Difficulties

Learn signs, causes, diagnosis, prevention, and treatment options for pharyngitis in koi fish, including swallowing...

Plant and Algal Toxin Poisoning in Koi Fish: Natural Pond Hazards

Plant and algal toxin poisoning in koi can cause sudden breathing trouble, weakness, and death. Learn signs, pond...

Pop-Eye (Exophthalmia) in Koi Fish: Causes, Severity, and Treatment

Koi pop-eye can signal injury, poor water quality, gas supersaturation, or infection. Learn symptoms, urgency,...

Predator Injuries in Koi Fish: Heron, Raccoon, and Cat Attack Wounds

See your vet immediately for koi predator wounds. Learn signs, diagnosis, treatment options, costs, and prevention for...

Protozoal Enteritis in Koi Fish: Intestinal Protozoa, Weight Loss, and White Feces

Protozoal enteritis in koi can cause weight loss, poor appetite, and white feces. Learn symptoms, diagnosis,...

Pseudomonas Infection in Koi Fish: Ulcers, Fin Damage, and Secondary Infection

Pseudomonas infection in koi can cause ulcers, fin damage, and secondary infection. Learn symptoms, diagnosis,...

Rectal Prolapse in Koi Fish: Why Tissue May Be Protruding From the Vent

See your vet immediately if tissue is protruding from your koi’s vent. Learn causes, symptoms, diagnosis, treatment...

Salt Toxicity in Koi Fish: When Pond Salt Becomes Dangerous

Salt can help koi in some situations, but too much can harm them fast. Learn signs, causes, diagnosis, prevention, and...

Saprolegnia in Koi Fish: Fungal Skin Infection and Cotton Wool Growths

Saprolegnia in koi causes cotton-wool growths on skin, fins, or eyes. Learn symptoms, diagnosis, prevention, and...

Saprolegniasis in Koi Fish: Cotton Wool Fungus, Causes, and Treatment

Learn how to spot saprolegniasis in koi fish, what causes cotton wool fungus, treatment options, typical cost ranges,...

Skin Flukes in Koi Fish: Gyrodactylus Infection, Flashing, and Skin Damage

Skin flukes in koi can cause flashing, excess slime, and skin damage. Learn signs, diagnosis, treatment options,...

Skin Flukes in Koi Fish: Gyrodactylus Symptoms and Treatment

Koi skin flukes can cause flashing, excess slime, ulcers, and weight loss. Learn Gyrodactylus symptoms, diagnosis,...

Soft Tissue Sarcoma in Koi Fish: Lump, Growth, and Prognosis Guide

Learn how soft tissue sarcoma in koi fish may look, how your vet diagnoses a lump or growth, treatment options,...

Spawning Injuries in Koi Fish: Reproductive Trauma After Breeding

Koi spawning injuries can cause torn fins, missing scales, ulcers, and infection after breeding. Learn signs,...

Spinal Cord Compression in Koi Fish

Spinal cord compression in koi is an emergency. Learn signs, causes, diagnosis, treatment options, and realistic 2026...

Spinal Deformities in Koi Fish: Curved Back, Kinks, and Mobility Problems

Learn causes, symptoms, diagnosis, prevention, and care options for spinal deformities in koi fish, including curved...

Spinal Deformities in Koi Fish: Scoliosis, Kyphosis, Lordosis and Vertebral Fusion

Learn signs, causes, diagnosis, prevention, and treatment options for spinal deformities in koi fish, including...

Spinal Fracture in Koi Fish

See your vet immediately if your koi may have a spinal fracture. Learn symptoms, causes, diagnosis, prevention, and...

Spinal Injury and Vertebral Subluxation in Koi Fish

See your vet immediately if your koi cannot swim normally, rolls, or has a bent spine. Learn signs, causes, diagnosis,...

Spinal Trauma in Koi Fish: Sudden Bent Body, Paralysis, or Abnormal Swimming

See your vet immediately if your koi has a bent body, paralysis, or abnormal swimming. Learn causes, diagnosis,...

Spring Viremia of Carp in Koi Fish: Signs, Risk, and Outbreak Response

Learn the signs of spring viremia of carp in koi, how it spreads, outbreak steps to take fast, and what testing,...

Squamous Cell Carcinoma in Koi Fish: Aggressive Tumors of the Skin and Head

Learn signs, diagnosis, treatment options, and prevention for squamous cell carcinoma in koi fish, including realistic...

Stomatitis in Koi Fish: Inflamed Mouth Tissues, Ulcers, and Treatment

Learn signs, causes, diagnosis, treatment options, and prevention for stomatitis in koi fish, including mouth ulcers,...

Thelohanellosis in Koi Fish: Intestinal Cyst Parasite and Weight Loss

Learn how thelohanellosis affects koi, including weight loss, intestinal cysts, diagnosis, treatment options, and...

Thyroid Hyperplasia in Koi Fish: Endocrine Causes of Throat Swelling

Learn why koi develop thyroid hyperplasia, what throat swelling looks like, how your vet diagnoses it, and practical...

Toxic Liver Disease in Koi Fish: Hepatic Damage From Waterborne and Feed Toxins

See your vet immediately if your koi is lethargic, off feed, or bloated. Learn signs, causes, diagnosis, prevention,...

Transport Injuries in Koi Fish: Shipping Trauma, Bagging Damage, and Stress

Koi can suffer transport injuries from shipping stress, rough handling, and poor bag conditions. Learn signs,...

Trauma and Injuries in Koi Fish: Net Damage, Predator Wounds, and Pond Accidents

Koi injuries from nets, predators, and pond accidents need fast care. Learn warning signs, vet options, prevention...

Trichodina in Koi Fish: Common Skin Parasite, Irritation, and Pond Management

Trichodina in koi can cause flashing, excess mucus, and breathing trouble. Learn symptoms, diagnosis, treatment...

Trichodina in Koi Fish: Skin Irritation, Excess Mucus, and Treatment

Trichodina in koi can cause flashing, excess mucus, and gill irritation. Learn symptoms, diagnosis, treatment options,...

Vertebral Compression and Fusion in Koi Fish

Learn signs, causes, diagnosis, prevention, and treatment options for vertebral compression and fusion in koi fish,...

Whirling Disease in Koi Fish: Myxobolus Infection and Spinal Signs

Learn how whirling disease-like signs affect koi, what Myxobolus infections mean, when spinal or spinning signs need...

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