Sequestrant?

[waterbear]

There are some products that increase the magnesium hardness of the water because magnesium scale is "mushy" and rinses off easily. Perhaps that is what he is trying to sell you. Whether they work to prevent calcium scale i cannot say.
There are also some sequestrants that have a high chelation index for calcium which ,after all, is a metal. Most sequestrants have a high chelation index for iron or copper and, while they will sequester some calcium anyway, it is not what they are designed for. My feeling is that these calcium sequestrants are most useful in areas of extremely hard water where the only other options are trucking in soft water or reverse osmosis filtration yearly. They do not eliminate the calcium but do 'inactivate' some of it if applied on a regular basis (just like any other seqestrant) to minimize scale buildup.

Then again, it could just be more 'snake oil'.

If you could post the brand and name of the product and/or the ingredients perhaps we could tell you more.

AS far as the salt test strips, the fast strips are made by LaMotte and the slow strips are made by AquaChek (Hach). I have never tried the LaMotte salt test strips but PoolSean did not seem thrilled by them. You can probably find them by mailorder on the 'net.

[Poolsean]

But then again, you can just test and ensure your water chemistry is balanced, according to the Saturation Index. This, along with the Self Cleaning feature of your salt system, should prevent calcium scale. As waterbear said, these chemical additives are more of a preventative product and can be quite an expensive option.

I love the guys at LaMotte and they have some excellent products. The quick read strips should (IMO) ONLY be used with a water sample under shade or indoor. So you can take a water sample then dip your strip once you're under shade, or dip the strip in the water, then go to a shaded location. If you do this in sunlight, my experience is that you have too short a window of opportunity to make your comparison. They are accurate enough, if you do it out of sunlight.