Just recently posted my experience somewhere else, but thought I'd copy and paste it here..
Thought I would give my impressions on the switchover to Fritz Reef Pro Mix (RPM). Its been about 3 months and its going quite well. Compared to RC, the salt granuals are of consistent size, and the mix is dry. RC has a bit of natural moisture to it, and this feels much dryer. As for how it mixes up, its about 1/2 cup per gallon of water (perhaps a touch more), very similar to RC. I cleaned my mixing tank before the switchover and I can tell you that it does not leave the residue in the tank that RC does (even after hours I mixing). As for the water chemistry and health of tank inhabitants, I have not lost a fish or invert. I picked up a bunch of new corals in November and I can see noticeable growth throughout all, SPS and mushrooms.
Hoping this info helps anyone considering a change. I will be sticking with this brand for the foreseeable future.
Happy reefing [emoji225][emoji226]