Yes,... SPS...:biggrin:

but why? I'm adding calcium chloride and sodium bicarbonate, not seeing phosphates in the recipe.

Well, if you want to be picky,... you can dose Foz Down (I have used it, too) to reduce phosphates, which helps SPS growth...

My point was really that how you dose Alk and Ca are not the only things that are important about good SPS health. And the OP did mention that he had an SPS dominant tank.

What is MB7? One of my biggest colony did die over night due to either alk or mg fluctuation when I was trying to fine tune them

Yeah, I don't want to mislead here. Big fluctuations on Alk are not good. But a change of 1 dKH will not kill your corals (have done that many times with no ill effects). Not sure what type of change you are talking about.

And with Mg, best to raise it only 100 ppm per day. I manually dose Mg every 3 weeks with my water change.

I dose MB7 every 2nd or 3rd day. It adds beneficial bacteria which prevents cyano and works well with your bio pellet reactor to prevent mulm and clumping. Plus it generally makes your water clearer in your tank, with less detritus on your rocks and sand. Here is a link for that.
http://brightwellaquatics.com/produc...robacter7t.php