pipe cleaner, the things with the metal wire core and the nylon fuzz around it, plus the alcohol/bleach/420 cleaner, try all of them, also, you could put a natural fungicide into the bong, like neem oil, and then rinse it out with the other cleaners.

or, find a genie, and get granted 3 wishes.

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when you learn to walk on the planes of existence, you can learn to run on the planet of earth

au revoir