Chalky Stuff at Waterline - What is it?

[Richs100]

I'm getting ready to do my first water change soon (1st fill was Thanksgiving)
Yesterday, I was in the tub (2006 HS Envoy) and noticed that there is a whitish, chalky like substance at the waterline of the tub all the way around.  It's not obvious because of the light color of the tub (Sterling Marble).  I can remove it with my fingernail and will use a nylon scrub to clean it off when I change the water.  
But, What Is It?

My water chemistry has been excellent.  Typically, pH 7.5, Alk 80, Calcuim 160 using a Taylor kit.  I use dichlor for both maintenance and shock with (very) occasional use of MPS, Ozone and Silver Ion cartridges (Nature2). Vermonter dosing method. Have been shocking about every 2 weeks, but only if needed.  Water quality has been great during this first cycle and I am changing the water because it's coming up on 4 months and CYA has now moved over 100.    
Any Ideas??

[Chas]

You are overdue for a water change.

Do that first, I bet this will go away.

The now famous "Chas' Law" states that a spa in motion tends to need a water change at the end of the first 30 days. After that, a four month interval is usually good.

White stuff is most often calcium, but if it is calcium you will usually also have a bit of it getting hard on the surfaces. Feel like sand. If it is not doing that, it might be soap and/or oils.

HTH

 8-)

[Richs100]

You are overdue for a water change.

Do that first, I bet this will go away.

The now famous "Chas' Law" states that a spa in motion tends to need a water change at the end of the first 30 days. After that, a four month interval is usually good.

I thought Chas' Law only applied to newbies.  (I had a Prodigy for 11 years before this tub)
I didn't realize I was in violation.  I will bring myself into compliance asap.
Is there a fine?

[hottubdan]

The fine is white chalky stuff at the waterline.

Remove substance and send to Chas immediately!