How's your Mg level? Your tank will require much more Ca and Alk to stay balanced if Mg is low.

I'm interested to know what you've got in that sucker too??? I've got basically the same water volume in my system as you do, w/ a good ammount of SPS and a clam. My tank only requires 25ml of B-Ionics daily. In my tank CA is 460, dkh is 10, and Mg is 1450. Those reading are at 1.026.

I made a very simple little DIY dosing pump system for two part that is waaaay easy to do, cost next to nothing to build, and has worked extremely well for me for over 6 months now. PM me for details.