about 3 weeks ago i noticed a small pen point spot that was an amberish color (rust?/dirt?) on the floor of the deepend of our 3 month old inground pool with maui gem quartz finish (blue lagoon color).
the spot was about 8" from the main drain, toward the center of the deep end. i took out the goggles and checked it out. looked like it was on one of the white speck areas of the quartz. i tried brushing but it didnt go away.
i popped on the forum and learned about the ascorbic acid process. so i took a vit c tab and rubbed it on the area and within a second it totally disappeared. i didnt think much of it until it returned today. same spot, same size, etc.
so my question...what could this be?
i was thinking the worst in that it was a rebar or tie spot, but those should be 3-4" into the gunnite. i was also thinking that if it was rust coming from metal in the shell that it probably wouldnt vanish so easily with just the touch of a tablet.
a few more bits of info, we have salt water pool at about 4000-5000 ppm (it is high because we got a double dose of start up salt)
perhaps this is interacting with a faint metal chip in the quartz?
thanks in advance for any thoughts, tips, etc.