Water Mold Disease (Saprolegniasis)
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About this condition
A fungal condition caused by Saprolegnia and related water molds that colonize wounds or weakened tissue, producing white to gray cotton-like tufts. It tends to develop in cold water or following injury and can spread if left unaddressed.
Common symptoms
- White to gray cotton-like growth on the body, fins, or around the mouth
- Redness or erosion at the affected site
- Sluggish movement or resting motionless at the bottom
- Loss of appetite
Common causes
- Water mold (Saprolegnia and related species) infection
- Wounds on the body surface or skin damage after spawning
- Low water temperature (especially below 15°C)
- Weakened immunity or poor nutrition
Prevention (husbandry & daily care)
Keep water temperature in an appropriate range (approximately 18–28°C) and avoid sudden drops. Prevent injuries from fighting or handling, and quarantine new fish thoroughly. When managing eggs, promptly remove unfertilized ones to prevent spread.
Related species guide
→ Browse the species guide for this animalWhen to see a vet
Consider consulting a specialist store within a few daysWhat can a specialist store do?
Managing the wound and improving husbandry conditions are the central focus when dealing with water mold. Consulting a specialist aquarium store or experienced keeper provides concrete guidance on assessing the affected area and reviewing water temperature and quality management. If egg infections are a concern (common on unfertilized eggs), experienced keepers can also advise on separating viable eggs from non-viable ones.
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