Possible Algae?

[Hurricane Gio]

Been real busy and have not had time to brush pool. Now form dirt and other organic matter blowing into the pool, I have black spots in the water, mainly on stairs, swim out and some spots on the floor. It's hard to brush off with a steel brush, especially on the grout lines. When brushed off, it's leaves a green spot. Is this algae?

Water has been balanced and real clear.
If it is, do I kill off with bleach or algae treatment?

Thanks

 

[chem geek]

Sound like it might be black algae. You might have poor circulation in those areas so when you aren't brushing the pool this slow-growing algae (technically, a cyanobacteria) takes hold. You can SLAM the pool and brush the affected areas regularly during the slam to expose the roots to elevated chlorine levels and that should kill it off.

 

[Hurricane Gio]

Thanks. Yes, outset stairs is the worse area.