Mike, welcome to MAAST!
I can also help to back Jim's findings. I am usually on the same regime as Jim since we work so closely together. I have found the fritz salt to be much better than the other salts, but a little slow to mix ( 1 hour @ 76 degrees in 100 gallon rubbermade tub with rio 2500 circulating) PH was 7.8, calcium 375ppm, this was all I tested on the last test. I have noticed the aquacraft to mix a little fast, but haven't noticed much difference in coral growth. I also use a kent 5 stage RO/DI/hi-s filter for both water changes and top-off. I am running a dual calcium reactor and Kalk reactor also so the PH in the tank doesn't change even with the slightly lower mix. Calcium is almost always in the high 400's. If you would like to send me a sample bucket of Fritz salt I'd be happy to change one system to Aqua Craft and one to Fritz salt and set up identical tanks side by side with identical equipment and note growth of frags, mushrooms, and so on under controlled conditions.
Tim Marvin
(512) 336-7258