I’ll run a full set of tests tomorrow morning. City waterA couple things you could do to help us narrow it down:
1 - Post a new full set of water test results. You can show them here and/or in your Poolmath log since it's linked.
2 - Try to rub a Vitamin C tablet on the stained area. It the Vitamin C tabs removes a stain, it's iron. On a well?
Let's start there and see where it takes us.
I'm the only one that works on it so no, I've never used algaecide or anything with copper in it as far as I know.ok, your FC is right on the border.....raise it up and keep it about 9-10 and see if over time and with brushing that will help. Its safe to swim in, so don't worry.
Has anyone added cheap algaecides or used copper in the pool?