I only have 3 hard corals and my montipora is the only one growing like a weed. Anyhow I was focused on alkalinity and my calcium dropped to 200 my corals looked horid . I brought it bake up with a 25% water change and added calcium til I was back to 400 . It took forever to get it back up. Corals look great but now my alkalinity is at 3.7 I did not have a problem with it till now. I guess I do not understand the calcium alkalinity magnesium pH relationship.