I think the fears of alk swings are overblown. Of course, you want to be reasonably consistent. I keep mine close to 8, but it ranges from 7 - 9 (as high as 10 sometimes) with water changes and as I adjust my dosing. My SPS growth and color have certainly not been affected.
And yes, better to dose alk at night to keep your pH up. And my Ca has been all over the place, too, from 380 - 480. It varies the most for me.
What I have seen, though, is the impact of higher phosphates. That seems to have a pretty immediate and lasting effect, and takes a while to get back to good growth and color.
If you want the best growth and color for your SPS, get the phosphates down to zero (as measured by the Hanna digital checker, not the color test kits). Plus your algae disappears then, too, so it much less work to keep your tank looking good. And don't forget your MB7.
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