Calcium and Magnesium Stability - Is it as Important as Alkalinity Stability?

[that Reef Guy]

So I know that everyone stresses to keep Alkalinity as Stable as possible for Chalices and SPS.

I have heard one person even say that you must keep it within 1 tenth of one point or your Corals will Suffer (So if your Alkalinity is 7.3 you must always keep it between 7.2 and 7.4 - No Less not More).

But I have never heard anybody say this about the other big two things to test for (Calcium and Magnesium).

I just always here keep your Calcium around 450 and Magnesium around 1350

But I have never heard anybody say you must keep it within X amount of points or your Corals will Suffer like I constantly read with Alkalinity?

So my question is do you have to worry about Stability with Calcium and Magnesium?

For instance if my Calcium was 450 today, then 430, then 490, then 410 the day after that does it matter as long as it is over 400?

Or do I need the Calcium to always be a Constant 450?

 

[Pete polyp]

Its best to keep them all as stable as possible. Alkalinity does have more of an effect on corals with instability. There's far less alkalinity in the water compared to the other 2.

Here's a good read

http://reefkeeping.com/issues/2002-04/rhf/feature/

 

[Reefing Madness]

Most would let the Calcium and Mag drop within their respective realms, meaning Cal between 380-460 and Mag between 1250-1350, and not have any issues going up or down within a few days.