Yellow staining around my mosaic

[grivera]

During the last couple of days, my 3 foot sea horse mosaic, which is on the floor of the shallow end, has yellow staining around the edges, it resembles rust and will not brush away. What could be causing this and what can I do to reverse it?

I also have a couple of specs that come and go on their own on one side of the pool. They appear to be rust but will go away sometimes for several weeks and return. Brushing will not remove them. I put "metal magnet" in about a week ago for the small stains and like in the past, it did not help?

My #s:

PH - 7.2
FC- 5.5
CC- .5
TA- 130
CH- 230
CYA- 35

 

[JasonLion]

Try holding a Vitamin C tablet against one of the stains for 30 seconds and see what happens. If it is an iron stain the stain will vanish around the vitamin C tablet.

 

[grivera]

I tried rubbing with a vitamin C tablet and also with a pumice (sp?) stone-no dice. What could it be?

 

[grivera]

BTW, I should have mentioned that I have never insttalled the Nature 2 cartridge in this pool for fear of metal deposits.

MODERATOR, please place this post in a more appropriate forum.