The store where I got my pool sells both pucks (cal hypo and trichlor) and bags supposed to be for shocking only. I ocassionally use the dichlor bags for my daily dose, even though the bag directs to use all at once, but I use it only when I'm raising CYA, as I have a small pool and can't see buying those large amounts of CYA packages; works great; only mildly acidic; and I keep it sealed; dissolves much better than cal hypo and doesn't cloud my pool or leave a residue like cal hypo does and takes only 1.7 fluid Oz per ppm in my little pool. The only issue is that I have to dose for a while, then test, then repeat. My pool doesn't seem to increase CYA at the pool math level, so I usually must use more dichlor than the math shows. The FC effect though, is right on the money.
I've seen them directing customers to the cal hypo pucks once they've achieve pretty high CYA, but I didn't know they dissolve quickly and wonder how they tell them to manage those pucks or what they tell them if the customer is at the upper range of CH and CYA, since they don't sell liquid. Of course they're like most stores and call for that under sanitizing 1-4 level irrespective of CYA, but at least they don't let them keep stabilizing until it's time to drain.