Originally Posted by
livedarklions
I only put water in mine. I will occasionally notice a little slimy feel if I haven't cleaned it recently, but no, there's no black stuff. Dirt get on the outside of my bottle, and that is often dark, but it's not slime.
I'm not claiming my bottles are sterile, but no, they're not dirty inside like that.
Yeah, straight water is probably not a great accelerator for growth. My bidons almost always have homebrew Gatorade in them: turbinado sugar, BCAA powder, pea protein powder, pink Himalayan sea salt, and flavoring. I like to feed my black-stuff premium fuel.