Interesting! I brush my pool once a week, since this started I have been brushing two or three times a week. I check my water chemistry twice a week. Why is it that the chlorinator asks for such high CYA and such low FC? Why couldnt I lower the CYA level? I just dont really want to run high levels of chlorine, so I can increase the chlorinator lifespan. I just checked my CYA again and it actually is closer to 60 than 70. The black dot test is a little speculative if you ask me.