My boss has a gunite in-ground pool with spots of Black Algae appearing in the pool. She uses either Tri-Chlor or Di-Chlor tablets exclusively for chlorination. I tested her water for her (I have the good Taylor kit), and here were her numbers:
CYA well over 100 (100 is the highest my test kit goes, and before I even got to the 100 mark, I could no longer see the black dot)
I am not sure what they use to shock, but I'm wondering if it is Cal Hypo, due to the high Calcium level.
I need to give her instructions on how to rid her pool of black algae. I know what to do, but she needs to hear it from the "experts"!