Quick referencePiscine mycobacteriosis (fish TB) is a slow chronic bacterial infection causing weight loss, ulcers, and skeletal deformity. Largely incurable; cull infected fish + protect humans (zoonotic).
Symptoms
Yellow/red ulcer
Weight loss / sunken belly
Spinal deformity
Refusing food
Color fade
Skin growths / nodules
Pop-eye
Cause
Mycobacterium marinum + Mycobacterium fortuitum. Slow-growing acid-fast bacteria. Spread via contaminated water, infected fish ingestion, contaminated equipment. Common in long-running tanks.
Treatment options
No reliable cure. No medication consistently treats fish TB. Some lab studies show Kanamycin + Erythromycin combos slowing progression but not curing.
Cull infected fish. Most reliable response. Use clove-oil overdose euthanasia.
Sterilize tank (severe outbreaks). Drain, 10% bleach soak 24 hours, rinse, dry 4-6 weeks before restart. Hard to fully eradicate from biofilm.
Permanent quarantine for survivors. If keeping survivors: never mix with naive fish. Carriers shed for life.
Always treat in a separate quarantine or hospital tank.
Prevention
Quarantine new fish 30-60 days. Avoid wild-caught feeders. Wear gloves when handling fish - mycobacterium marinum causes "fish tank granuloma" on human skin (slow-healing painful nodules requiring antibiotics).
Fatality + outcome
Slow but progressive over months to years. Long-running tanks may have asymptomatic carriers. Eventual mortality high.