New user with old vinyl pool

[markwg]

First post

Thanks for your response. I do check for stabilizer, and added some this spring. I had ask about using metal free when I agreed to install the frogger, and was told it would not be a problem. So, a contradiction but I believe you and will stop using the metal fee. I live in the country with fields front and back, and was told that farmers spraying was probably the source of the phosphates. I have a test kit and check for phosphates every week.

Couple questions please;
Do I need to chlorine shock every week? If so, can I use non-chlorine shock, or alternate between the two?

I have some yellow stains on the white portion of the liner above the water line where it meets the coping.
Any suggestions about how to remove them?

Thanks -