I posted this in another section but didn't get anybody who recognized it. I haven't ever battled algae (well once had mustard algae after a hurricane but it went away with yellow out and hasn't come back). Does this look like algae? I thought you could tell if it was algae because it would brush away but come back. Could this be metal staining? Water numbers all look great except CYA (I have the good test kit - never have the water tested at the pool store) and I'm finishing up a partial drain to rectify this. This picture is of the spa but the whole pool has this. It has slowly built over time.
I've lurked here for a while and gotten some great advice...thanks in advance for your help.[attachment=0:279nj18o]pool.JPG[/attachment:279nj18o]