Thanks for the info. It doesn't seem to be dissolving any quicker now that the water is cold than it did a couple months ago when it was warmer (tank temp is running about 58-60 degrees). 1 teaspoon Gh Booster in my 75 gal tank takes at least 3-4 hrs to dissolve .. my 20 gal takes 5-6 hrs both may take longer but it gets hard to see when the lights go out.The component in the gh booster that can't dissolve dissolves better in cooler water, not hot water. It's:
I prefer to replace some of my CaSO4 with CaCl2. It absorbs water very readily but it dissolves much easier. However, there's nothing wrong with being unable to get the calcium sulfate to fully dissociate...it'll do it over time.