Pete, Our microbiologist has tested the effectiveness of bleach on mycobacteria and found it doesn't kill myco. We use nolvasan or maxima. Aaron ----- "Fish TB" is caused by mycobacteria. Sadly, the best treatment for mycobacteriosis in fishes is to dispose of the fishes, discard the contents of the tank, and sterilize the equipment with household bleach diluted to 10%. Pete Mohan, Kent, Ohio-------