Saprolegnia is a water mold that produces white cottony patches on fish, especially on existing wounds or weakened tissue. Common in cool-water fish (goldfish, koi).
Existing wound + low water temperature + organic-rich water creates conditions for fungal colonization.
Always treat in a separate quarantine tank.
Treat wounds promptly. Maintain pristine water. Avoid handling fish roughly during transfers.
White cottony or fuzzy patches on body or fins. Patches on existing injuries. Lethargy in advanced cases.
Existing wound + low water temperature + organic-rich water creates conditions for fungal colonization.
API Pimafix or Fungus Cure: OTC fungal treatment for 5-7 days. Effective for most Saprolegnia cases.
Treat wounds promptly. Maintain pristine water. Avoid handling fish roughly during transfers.
Mild to moderate
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.