I learned about homebrew and fermentation when I left gatorade in the camelback the first yr I used one. Really hard to clean. Algae grows in gator or powerade even in the frige once the bottle is opened, so don't leave it there, unless you freeze it, for more than a week or two. Now I only use water, and even then biofilms of some sort, hopefully algal but probably some mix of that and which ever of the dozens of oral bacteria that reflux back into the water when you drink survive. I also found there are at least two diameters of long flexible brushes for the tubes, one of which was a fraction of a millimeter too small and does not clean Blackburn tubing! It just slides back and forth. Brushes are useful when the biofilm gets a bit tenacious and won't let loose. Steve