Identification
White, gray, or pale fuzzy patches on mouth, lips, or jaw.
Often accompanied by reduced appetite, lethargy, frayed fin edges.
Why Not "Fungus"
Flavobacterium columnare bacterium, not fungal. Spreads fast in warm water.
Antifungals (like copper) do not work. Broad-spectrum antibiotics do.
Treatment
Furan-2 + Kanaplex combo. Dose per package for 7 days.
Drop temperature to 75°F — columnaris worsens in heat.
Large water changes during treatment. Remove carbon from filter.
Prevention
Quarantine new fish. Maintain water quality. Avoid overcrowding.
Most outbreaks trace to stress + high temperature + poor water.