bacterial systemic · both

Fish TB (Mycobacterium)

Fish TB (Mycobacterium marinum) is a slow-progressing bacterial infection that causes weight loss, bone deformities, ulcers. Zoonotic - can infect humans through skin cuts. Almost always fatal.

Severity: CRITICAL - usually fatal + zoonotic risk to humans

Symptoms

Cause

Mycobacterium marinum bacteria. Chronic infection from contaminated tankmates or substrate. Long incubation (months).

Treatment

Always treat in a separate quarantine tank. Most medications are toxic to coral, invertebrates, and live rock biology.

Euthanize affected fish. Fish TB is essentially incurable. Most ethical action is humane euthanasia.
Antibiotic combos (rare success). Some hobbyists try kanamycin + erythromycin for 4-6 weeks. Success rate <20%.

Prevention

Quarantine + don't reuse substrate from infected tanks + sterilize equipment with bleach. Wear gloves when handling sick fish.

Related

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.