I ordered Marco sand four years ago. It was the Bahama Aragonite sand (fine) and came in 20 lbs bags. It took a few days for the water to clear: I probably did not rinse it enough, and I really had nothing else to compare it too so this may be normal for a new tank.
I have not had a problem with sand storms. If I point the power heads directly at the sand it redistributes itself rather quickly. I also have a large engineering goby that has totally rearranged all the sand (not to my liking). No problems with a sand storm, it settles quickly.
I did not weigh the bags, they were marked as 20 lbs each.
This was for my 90 gallon build. I will use them again for my 180 build.