Fish disease library

Browse every disease, parasite, and bacterial infection covered in our knowledge base. Filter by symptom, fish type, or pathogen.

Freshwater Tropical

Cloudy Eye

Hazy or opaque film over one or both eyes — usually a sign of bacterial infection or chronic…

Moderate

Freshwater Tropical

Swim Bladder Disorder

Loss of buoyancy control — fish floats, sinks, or swims at odd angles. Common in fancy goldfish and…

Moderate

Freshwater Tropical

Dropsy

Bloated body with pinecone-stuck-out scales — a symptom of organ failure, not a disease itself. Prognosis is generally…

Critical

Freshwater Tropical

Velvet (Oodinium)

Dinoflagellate parasite producing a fine, gold-dust coating across the body. More lethal than ich; gill infection causes rapid…

Severe

Freshwater Tropical

Fin Rot

Progressive deterioration of fin tissue caused by opportunistic bacteria — usually a symptom of poor water quality.

Mild

Koi & Pond

Koi Herpes Virus (KHV)

Notifiable viral disease devastating koi populations worldwide. Mortality 80–100%. No cure — only management and prevention.

Critical

Marine / Saltwater

Marine Ich (Cryptocaryon irritans)

Saltwater white-spot disease. A 2006 resistant strain renders traditional copper and formalin treatments ineffective — quinine sulfate is…

Severe

Freshwater Tropical

Hexamita (Hole-in-the-Head)

Intestinal flagellate parasite causing pitted lesions on the head and lateral line, especially in cichlids and discus. Often…

Moderate

Freshwater Tropical

Mycobacteriosis (Fish Tuberculosis)

A slow, chronic infection caused by Mycobacterium spp. Symptoms include emaciation, spinal deformity, and granulomas. Zoonotic risk —…

Critical