Pool liner feels like sandpaper

[PoolDoc]

I'll offer a more extended reply later, but for now.

1. Do NOT try to scrape the scale off: you can damage the liner.
2. Do get a K2006; you are going to need to the full test capability to manage the liner clean up.
3. Do get your chlorine up and kill the algae; that has to be done first.
4. Please complete the PF Pool Chart, to allow us easy access to your pool info:

Pool Chart Entry Form
Pool Chart Results

5. Finally, DO get your pH DOWN. You want it just barely above the LOWEST point on whatever tester you have.