I purchased a new house late last July that is 27k with a pebble stone finish. The pool was a complete swamp and had to be drained. Once I had it drained and shoveled out I cleaned the pool with a stiff bristle brush and diluted bleach. At that time some dark stains (more on the black side) remained from my cleaning efforts, especially on the walls where it looks like 'runs'.
The pool guy told me that any stains that were left would disappear over time with the chlorine and I trusted that. I didn't perform an acid wash on the pool because I heard it could take years off the finish. Fast forward to almost a year later and the dark stains are still there. They don't look that bad when the pool is running and the water is moving but when all of that stops you can definitely see them clearly. I just opened the pool a little over a week ago and went through a full shock using bleach. The pool has an SWG and I'm about to move to using that system over bleach.
Any idea how to combat this without draining the pool and performing an acid wash? The stains in the one pic look a little darker than they actually are.