Waterline algae

[cfischer]

My water is crystal clear. My FC is 6.0. MY CC is 0. I did the overnight chlorine test and it didn't move. No signs of visible algae except at the waterline of pool. I scrubbed it off with a brush and a week later it was back. What's going on?

FC 6.0
CC 0
CYA 60
TA 100
PH 7.4
CH 300

Thanks,

 

[Bperry]

My water is crystal clear. My FC is 6.0. MY CC is 0. I did the overnight chlorine test and it didn't move. No signs of visible algae except at the waterline of pool. I scrubbed it off with a brush and a week later it was back. What's going on?

FC 6.0
CC 0
CYA 60
TA 100
PH 7.4
CH 300

Thanks,

What’s your chlorine levels been like the past few weeks?

 

[cfischer]

Up and down 3-6 FC

 

[Rancho Cost-a-Lotta]

Can you describe what you're seeing, or better yet, take a few photos.

You should do an Overnight Chlorine Loss Test.

I see you already did an oclt.

 

[Newdude]

CYA 60

Up and down 3-6 FC

You're flirting with disaster and that's why you're seeing algae. You want to dose to 10 so that when you lose 3, you're still in target range. Once daily loss is down to 2 soon, then you can lower the target to 9 for the same effect.