Here is the low down.
Had our pool renovated in 2001 when we moved into the house. It was a swamp, unused for years.
Started getting little stains in it after a few years. I figured it was leaching through the back of the plaster.
Hurrican Ike comes along, much sandy dirt from the greenbelt I live on. This sand has a slight red tinge to it, it's mostly a tan, but a slight red tinge to it.
After power was restored (16 days) and i got the pool cleaned up, I realized the stains were much worse. And the stains were about the same design as the dirt that was on the pool bottom. So i figured maybe it was not leaching through the plaster, but just dirt, maybe iron.
So I got the vitamin C (absorbic acid) tables, and placed on a really dark spot (but I figured some of those freckles were organic, not iron), but the staining did clean up (see the whiter circle around that split brown spot inside the red circle)
You can see it has improved.
Here is a picture of the middle of the pool.
And the deep end
I tried dropping some more tablets in parts of these areas, and they seem to have lightened them also.
So for a 30K gallon pool, what do I have to do to remove these stains?
Where do I get Absorbic Acid the quantity i would require?