I believe MB is known to kill off BBHello; Too bad you do not have a suitable hospital tank right now. I have been in that position a few times. I was going to suggest a few days in a solution of methylene blue. Not sure if the methylene blue is still available. It use to be a suggested treatment for fungus problems. It is a dye and will stain some things. There may be other products to do the same thing.
Good luck
