Fish showing a general cotton-like appearance and color matching suspended materials in water indicates which condition?

• A. Whirling disease
• B. Costiasis
• C. Acidosis
• D. Fungal infection

Answer: (D)

Cotton-like, fluffy growth on fish is a classic sign of a fungal infection, typically saprolegniasis caused by water molds such as Saprolegnia. The white to gray cottony tufts are fungal hyphae that colonize damaged skin, gills, or wounds and can appear to drift with suspended particles in the water. This overgrowth is favored by stressed fish and suboptimal water quality, which allow fungi to take hold. Other conditions produce different signs: whirling disease causes abnormal swimming and deformities, costiasis (a protozoan infection) irritates the skin and gills without forming the characteristic cottony filaments, and acidosis is a systemic imbalance with signs like rapid breathing or lethargy rather than surface fungal growth. So the described cottony appearance and drifting material best indicate a fungal infection.