I'm curious regarding this scenario. Let's say a particular pool has a mustard algae problem and it was properly addressed. If this pool were to drift below safe levels of the FC, would it get mustard algae again? Regular one? Both?
And in more generic terms - what is the actual source of algae of any kind? Let's imagine that there is a pool with virgin clean water. If we let it go, how does it start developing algae and where does it come from?