It's a balancing act between calcium and alkalinity. Reefs have several chemical/biological balances that need maintaining and if you grow hard corals, this is a major one. Only two or three chemicals are involved here, adding calcium with a reactor or chemically to keep the value high as hard corals will deplete it. If you only have a few hard corals, supplementing isn't needed as modern salt mixes generally have all the calcium you need. Alkalinity can burn corals and allow ph to swing wildly if allowed to get too low. I shoot for a dkh
of 9-12 and a calcium above 500ppm. Test and add supplements as needed over at least a week, no sudden changes, if calcium is okay, just add alkalinity until it gets where you want it. BRS has excellent info on this and sells the components for the solutions for far less than the packaged solutions at the LFS
. My best guess is that a bit of properly prepared baking soda would set your alkalinity right.
Last thing, when you start growing concrete hard pink algae everywhere and are cursing it while trying to get it off...you have created optimum conditions for hard corals to grow.