Wingo,
This is not Tuberculosis. Tuberculosis is totally different. Yes Mycobacterium marinum is part of the mycobacterium family in which tuberculois shares the same genus, but it is NOT in any way OPEN tuberculosis. Not even CLOSE to being tuberculosis. Two totally different things.
THere is no such thing as OPEN TB. THere is a milliary TB (systemically disseminated) and good ol pulmonary TB. Tuberculosis is a disease of the pulmonary system which has different characteristics all together. Trust me on this one...
Acutally, mycobacterium marinum is not very contagious to humans. Usually occurs in people who are immunocompromised in some way (cold, flu, on immunosuppressive drugs, etc) and by way of a
break in the skin. Hard to treat once you catch it because it is not your stardard organism. It's a mycobacterium which has different wall structure than most of your oridinary bacteria. Need debridement and special antibiotics to treat.
Best way to prevent it is to either wear gloves or to be very meticulous about washing your hands with soap and water each time you put your hands in the tank bare. Most noticable if you have a open cut that is just not healing over some time.
Just gotta be careful. This is a bug the Infectious Disease guys in medicine have known about for years. It is not new, but is very rare...