Acid wash it with a presure sprayer.
by a chemical called stain out or by using a pumice stone.
Have a look at this web page: http://www.stone-advice.com/latest/removing-stains-from-stone.html
Between the sun ad the addition of chlorine kept at somewhat higher levels they will eventually disappear. k
Lighter color fabrics will always so stains more easily. The bedskirt is however at the very bottom of the bed and is harder to notice then say, the comforter.
It sounds like some sort of algae when you expose it to the pools water it brings it under controll.
Shout removes stains from jam, grass stains, coffee stains, ink stains, blood stains, motor oil stains, etc.
Since you cannot remove the "stains" with the methods you have tried perhaps the stains are from too much acid or high acid levels. Are there also copper colored stains as well? Do you have a pool heater in the system? If so, then it is copper stains from an acidic pool water. The over acid conditions are stripping the copper from the heater copper tubing. k
Grass stains or food stains.
I seriously doubt that the pool sweep is the problem here with your stains. You will have to describe the stains in order to get to the root of the problem. Are the stains: Rust color or brown? Black or gray? Green? Blue? Are the stains consistent or uniform? Are they all over the pool? Do they cover the whole pool or are they in small patches? Answer these questions and I may be able to tell you the cause. k
Ah, this pool is beyond saving with normal procedures of chemical treatments with the water in the pool. It must be drained and cleaned possibly using various or several methods.
This must be an algaecide of some sort possible a low grade of chlorine. Did you follow the instructions EXACTLY? Is this product supposed to settle on algae spots? If not , did you brush it to keep it from clumping and settling on the bottom of the pool? The black stains, possible caused by the product burning the plaster where it settled --- improper use of product. Impossible to know without seeing the stains and finding out just how you used the product. Contact Bioguard for further info.
Stains