FC 4, CC 0, CYA 40, TA 80, CH 200, PH 7.8
Pool at 85-88 degrees all day long (full sun all day).
Chlorine is keeping up and not dropping below 3.
My pool is perfectly clear. Pool is a brown pebble tech. I noticed on the entrance to the skimmer from the pool about a square foot the pebble tech was greenish. I took a brush and it easily brushed off. Stupid question...is this Algae? What are my next steps at this point? How do I prevent this?