This is just my exprience with IAL. I have hard water and my KH stays above 4. I use IAL in my 150 gallon cause I like the way the water looks and my cory's, Dojo's, Fire mouth, and Green terror love them. With that said I have no PH swings. I think its like one IAL for every 10 gallons, not sure who came up with that but its what I have read....
I break them up and put them a a glass jar, add boiling water, let sit for a few hours, then dump it into my tank.
Maybe someone with a little more insight will jump in and give us both some more info.