I have a 2 year old 75 gallon mixed reef very heavy with LPS and softies. My NO3 is 0.3 PO4 is 0.05 calcium is 399 magnesium 1455 Alkalinity is 13.5. I dose All For Reef and Bacto-Balance. My problem is I can't get my alkalinity down! Any help greatly appreciated. Thanks for your time with this.