Also called mycobacteriosis
Can spread to people. Zoonotic. Mycobacterium marinum causes 'fish tank granuloma' (aquarium granuloma) in people: it enters through cuts or scrapes when skin touches contaminated tank water or fish. Signs appear about 2-3 weeks (sometimes a month or more) after exposure: a red to purple bump on fingers, hands or elbows that grows into a painful nodule, may ulcerate, and can spread up the arm in a line. It is treated with antibiotics, often for several months; it can reach tendons, joints or bone and is harder to treat in people with weakened immune systems. Wear rubber gloves for tank work or wash hands and arms thoroughly afterwards, and see a doctor about skin bumps that do not clear (mention aquarium contact).
Non-tuberculous Mycobacterium species, including M. marinum, M. fortuitum and M. chelonae: slow-growing bacteria that cause chronic granulomatous disease, respond poorly to antibiotics, and can infect people (mainly M. marinum through skin breaks).
No effective treatment eliminates mycobacteria in fish; infected groups are usually culled (depopulated). Get a vet/lab diagnosis. Disinfect an infected tank before adding new fish: bleach to remove organic matter, then 70% ethanol or a phenolic disinfectant, because bleach alone does not kill mycobacteria.
If a fish is badly ill, talk to an aquatic vet.
Quarantine new fish; remove dead or dying fish promptly (fish catch it by eating infected tissue, contaminated food and debris); keep oxygen, pH and organic load in good order; UV sterilisation can reduce bacterial counts; wear gloves and wash hands and arms after tank work.
7 facts checked with sources
100 species
