Subject stays it. I always get some dense very localized dark green growth in seams where stairs meet liner and around pool light another seam crevice. A quick brushing breaks it up and vanishes.
I assume this is due to low circulation/debris collection here. Anyway this is first year of BBB method and thought (hoped) I may not have the issue this year. Full disclosure I haven't been brushing and I probably should do it more regularly, but pool is crystal clear otherwise.
FC has been consistently around 8 or bit more with CYA level of about 50-60. FC consumption doesn't seem out of line and I pass the OCLT. Yet this stubborn stuff still seems to be able to grow.
Normal and have to live with it? Or start shocking?