Anyone use or try one of these.
Purity Pool OS Out Spot Stain Remover
The Out Spot is a self-contained underwater stain remover. The cup holds about a cup of muriatic acid. Once filled and connected to a standard pool maintenance pole, the Out Spot can be lowered down to the pool surface and placed on top of a stain. Since acid is heavier than water, the acid seeps through the pad (slowly diluting, so go for the worst stains first!) over a period of about 20 minutes. Most stains are gone in seconds!
http://www.ebay.com/itm/110949178757?ss ... 1438.l2649