Mouth rot is a bacterial infection that causes white/grey patches around the fish mouth, eroding lip + jaw tissue. Often confused with fungus; aggressive variant kills within days.
Stress + poor water quality triggers bacterial overgrowth (Flavobacterium columnare). Often follows minor injuries.
Always treat in a separate quarantine tank. Most medications are toxic to coral, invertebrates, and live rock biology.
Pristine water + reduce stress + treat injuries promptly.
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.