I'm curious about the nature of FC loss. I know that algae will eat FC like popcorn. And if your CYA is zero, sunshine will, too. But what else affects FC? I've seen mention of "organic debris". I would assume this to be things like leaves, bugs, grass, etc. How about rain water? Tap Water? How do those affect it? Does FC drop faster at high levels vs low levels? For example, if you keep your FC on the high end of the range, will your bleach usage be higher than if you kept it closer to the lower end of the range?
ETA: Is there a resource that defines this somewhere? If so, please point me in the right direction.