Hello everyone I am the owner of a 20 year old pool. My pool has been green for the past 2 years so I decided to pump it and i got a new filter. When uncovering it i sa a huge stain on the bottom. It is greyish green and it is big. If only i can add a picture. Our pool is 26000 gallons. Can any of you tell me what kind of stain it is or how to solve it. Im looking into getting a service to acid wash. Or is it a smarter idea just to paint over it. I like the idea of painting it. It is a colored plaster pool. If you need any other information or have an idea please feel free to reply. I need help!!!