Velvet Disease (Oodinium)
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About this condition
A parasitic infection caused by Oodinium, a dinoflagellate that attaches to the skin and produces fine, gold or brownish dust-like spots. It is highly contagious and can spread rapidly to multiple fish in a tank.
Common symptoms
- Fine gold or brownish dust-like spots on the body surface
- Rubbing against substrate or tank walls
- Clamped fins and listlessness
- Rapid or labored breathing, gasping at the water surface
- Loss of appetite
Common causes
- Oodinium (parasitic dinoflagellate) infestation
- Stress from sudden or low water temperature changes
- Weakened immunity due to overcrowding or poor water quality
- Introduction via new fish, plants, or equipment without proper quarantine
- Insufficient quarantine of new additions
Prevention (husbandry & daily care)
Always quarantine new fish in a separate container for a set period before introducing them. Maintain stable water temperature and avoid sudden changes. Prevent overcrowding and keep water quality high with regular water changes.
Related species guide
→ Browse the species guide for this animalWhen to see a vet
Consult a specialist store or experienced keeper promptlyWhat can a specialist store do?
Veterinary clinics specializing in ornamental fish like medaka are limited, so the immediate priority is stabilizing water quality and temperature while isolating affected individuals. Consulting a knowledgeable aquarium store or experienced keeper can provide specific guidance on identifying the cause and reviewing husbandry conditions. When infection has spread through the tank, advice on isolation strategies and tank management to protect healthy fish is especially valuable.
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