My calcium has been around 500 and kh has been at 12, and ph 8.1. The system has been up for 4 months now and all sps frags (around 14 frags) are doing fine. It is a bb system. I postes a similar question a bout a month ago and have turned my reactor off. I change 10 gallons of water a week my calcium is now at 480 anf kh is 8. Much better,but why is my calcium being used up more? I've been using Kent salt. Most of the rock was dried base rock (free and no critters) so now I'm starting to get a little coraline growing on it. Should I be concerned?