I fought with this for 3 weeks when I got my new tub.
All that really matters is where you pH is at. Alk is ONLY a buffer to keep the pH more stable if it bounces around.
However many people such as us cannont get ph AND alk both in normal ranges at the same time.
So...........Get your pH down to where you want it with pH decreaser and do NOT WORRY about your alkalinity IF your pH remains stable. Screw alkalinity, what good is a buffer if your pH is too high! see my point?
I am sure I will get flamed, but this is what works for me and is the ONLY way I can get my pH to stay 7.4-7.6. My alk is about 50-70, but I don't give a damn cuz my PH is stable and i have no other way to do it.
Also if alkalinity is high, it is VERY hard to lower the pH unless you put in a LOT of ph decreaser. So dont be surprised if you have to put in several tablespoons to lower it. I would not put in more than 2 tbls at time until you notice some pH drop, because once the alkalinity drops to about 60, the pH will come down quickly.
Neo