Freshwater ich is caused by Ichthyophthirius multifiliis, a ciliate parasite that produces white salt-grain spots on freshwater fish. The most common freshwater fish disease.
Introduced via new fish, plants, or decor. Stress from poor water quality or temperature swings triggers outbreaks of dormant parasite populations.
Multiple effective treatments exist. Pick based on your tank type, livestock sensitivity, and severity. Always treat in a separate quarantine/hospital tank - most medications are toxic to coral, invertebrates, and live rock biology.
Quarantine new fish for 14 days minimum. Maintain stable temperature (avoid swings >2°F). Don't crowd fish - stress is a major trigger.
White salt-grain spots on fins, body, gills. Flashing or scratching against rocks/decor. Clamped fins.
Introduced via new fish, plants, or decor. Stress from poor water quality or temperature swings triggers outbreaks of dormant parasite populations.
Heat treatment: Raise tank temperature to 86°F (30°C) for 14 days. Speeds up the parasite life cycle so it cannot reproduce. Only safe for fish that tolerate high heat (most tropical fish do; goldfish, dwarf shrimp, and some plants do not).
Quarantine new fish for 14 days minimum. Maintain stable temperature (avoid swings >2°F). Don't crowd fish - stress is a major trigger.
Moderate - usually treatable if caught early
Always treat in a separate quarantine or hospital tank. Most medications are toxic to coral, invertebrates, and live rock biology.
Browse the full disease database for 45 aquarium conditions with treatment protocols, or check the care library for prevention-focused husbandry guides. Use our symptom matcher to rank likely diseases from observed signs, the water parameter checker to diagnose related water-quality issues, or the QT timeline calculator to plan a treatment schedule.