Quote: 10x later . . . LOL tongue is falling off . . . .
Black defines a color, I'm not aware that it defines a specific mold. I've never seen black mold in my waterers. A forgotten bucket has developed a red or pink slime . . . . but honestly I've not seen black on my buckets.
Concerning the water, mold would be a concern (or the slime) that forms at the rim because it provides a medium for bacteria to grow. What I tell my boy is if it is not squeaky clean, then it isn't clean. No matter how it looks.
It would take too much ACV to drop the PH enough to deter bacterial growth. Enough to be effective would make the birds not want to drink the water. ACV is one of those truths that gets passed around but has no real effect concerning the water.
George-- from my own personal experience-- my waterers do not grow that slime. THey stay sqeaky clean between cleanings. I'm talking about the inside that holds the water supply. No slime at all.