What uses up Mg? How fast should it drop?

[westwind77]

I was curious what, in a marine system, uses up the Mg? Fish, Coral, LR, Live Sand, All the above? How fast should Mg drop or be used up in a system? Should regular water changes keep or stable or is dosing needed? What is important to keep it stable?
Thanks!

 

[stanlalee]

everything that utilizes calcium. they are utilized at a calcium:magnesium ratio of 20:1 so it should drop MUCH slower than calcium. if you arent needing to add a bunch of ca your mg shouldn't be dropping either (unless your salt is low in mg to begin with which many are).