Spotted dark-green algae

[southflorida427]

Woke up to clean water with many spots on dark green algae.
Spot of algae gets removed with a brush and the spot keeps floating in the water (does not dissolve).
Total chlorine reads zero, free chlorine was also near zero.
I started SLAM, but I'm curious about this type of algae. Usually in the past when I got algae was a green water pool, this time its clear and doesn't read on the test.
Ideas?

PS: would send pics but I brushed it off before thinking about posting.

Update: welp, upon further reading, I think it's black algae...

 

[Texas Splash]

Starting the SLAM Process was the right move. Not so sure about BA, but if it is, be sure to scrub the areas where it may have tried to root into the plaster. Hopefully you got it in time before it could penetrate.

 

[southflorida427]

I'm still getting zero as CC, FC was 17 last night before going to bed and 14 in the morning around 9 am EDT.
30-40 CYA.
No visible algae today.

 

[Texas Splash]

No visible algae today.

That's good. Be vigilant as some algae could be hidden. Since you weren't able to check the FC until about 9:00 AM, the OCLT would not be valid. Maybe next time you can get that morning test done before the sun hits the water. Otherwise you might lose a little FC waiting that late.