Brown spots on pool bottom

[radiation]

I've recently noticed patches of brown spots on my pool bottom in the deep end. Neither brushing nor vacuuming remove the spots. My current readings are:

FC: 10.5
CC: 0
pH: 7.2
TA: 210
CH: 380
CYA: 90

Does anybody have any idea what the spots might be and how I can get rid of them?

 

[reebok]

you can try putting a vitamin c tablet on them.
pool-school/metal%20stains

 

[duraleigh]

Yeah, iron would be my guess but it's only a guess. Holding the vitamin C tab on the stain for a minute or two should confirm it if it's iron. If the Vitamin C has no effect, high FC levels will most likely cause it to fade away in time. Can you post a good pic?