There was something I read on another forum about the Tm pro reef salt being developed for tanks with calcium reactors. I think if you go onto the TM website they explain this? I ran TM pro reef for about 6 months. My PH always seemed to run a bit higher in it's high swing side, about 8.56. I've since switched to RC and my parameters seem better. One think I have noticed is for a 10 gal waterchange the TM pro took 4 cups and the RC takes 5. So the cost is probably justified as the TM pro seems to be more concentrated. Just my observations.