Hi guys. Bought an existing house with existing pool last month. Since then have been a religious follower of BBB method and have seen noticeable improvements in water clarity since taking over from previous owner's pool guy.
However, even though the water is sparkly, the pool is old and struggling cosmetically. Here are a few pics (underwater camera) of the ugly stain I'm trying to tackle:
First off, my numbers:
My original thought was I had some sort of algae problem, so performed the OCLT. Passed with no loss, clear water. I then tried the Vitamin C test and saw no results after a minute of holding tablet to stain. So just tossed tablet in water. Came back 30 minutes later and found the stain totally removed from the spot it landed. Repeated again with new tablet - same results.
So I'm thinking metal stain and am in the process of lowering FC to start the absorbic acid process. Does this seem a reasonable conclusion and approach?