Why is my PH unstable? - Page 2

I never run my FOWLR tanks at that high of salinity. Found it to be unnecessary. I keep them in the 1.021-1.023 range. Even using plain Instant Ocean and keeping the lower salinity, I've had good coralline growth and stable parameters. The extra Ca and alkalinity buffers in the Reef Crystals (or any "coral/reef" salt) really isn't needed because there aren't any corals to soak it up. Sure, cleaners and coralline will use some, but not a significant amount.

I am just saying' if you increase salinity you increase the bioavailability of those elements which produce more coralline algae. Not that running a fish only system at 1.026 is a bad thing or unnecessary. That's up for the op to decide, yes? 

Increased ca and alk levels in a fish only system don't hurt a thing as long as ca and alk are balanced/ proportionate to one another. Which if you just rely on water changes, it should never become a problem. 

If it were me I would continue to monitor Ca and attempt to keep it around 400ppm.  I would also continue to monitor Alkalinity and keep it between 3.0Meq/L and 3.5Meq/L.

If your tank doesn't settle down, you may need to test and adjust your Mg level.  Ca, Alk, and Mg are all interrelated and have an effect on your pH as well.