Water Clarity - Need Education

[szampino]

I'm posting this in the metals/stains forum because I have metals in my pool and have them under 'Metal Control'. I want to make sure that the information I get is relevant to a pool with Metals.

I've gotten my pool clear but I'm having trouble determining if it is Crystal Clear. There is a very suttle dull distortion to the water keeping me from saying that it is crystal clear. Can it be crystal clear? Or is the dull distortion something I'm going to have to live with because of the 'Metal Control'.

Numbers:

FC 2.5
CC .5 (the 10ml solution turned the slightes shade of red, and 1 drop made it completely clear)
TC 3
PH 7.2
ALK 90 - 100
CYA - about 10 (is there a way to measure below 20?)

Q. What does things like Polysheen/Blue stuff do? Is it reccomended? Will it mess up my water balance?