How important is Mg in a properly balanced tank?

[BillyZ]

my system is coming up to it's 2 year birthday. A month or so back I added my first corals; a rock with two types of mushrooms. The day after adding them to the system they were in FULL bloom, better than they looked in the LFS. About a week later I noticed them splitting and multiplying like wild fire and still in full bloom. Things looked great up intil about a week ago when I did the first water change since I got them. Ever since then the mushrooms have been very flacid. They hardly expand at all when the lights come on. Here's the readings:

sg: 1.023
Temp: 83f
amonia: 0
Nitrites: 0
Nitrates: 0
Ca: 400
Alk meq/L: 2.8

but I don't have a Mg test kit. all of my other parameters look spot on and don't really fluctuate (other than SG as don't yet have an autotop off)

The water change was 5 gallons (on a 55 tank) with CoraLife salt mix. I've heard this can be a touch and go mix but the new mix looked good on what I have test kits for. In the whole skeem of things, how important is Mg to a healthy reef system? Are they more important to certain types of hard/soft corals?

 

[reefrunner69]

MG is very important in the scheme of things, although it is not easily depleted from the system. Just a hunch, if your able to maintain CA levels above 350 then your Mg is fine. Mg deficiency is usually noticed by an inability to raise the CA and a high ALK.

I could be mistaken, but I believe that coralife uses borate rather than carbonate for it's buffer, in which case you alk is not indicitive of what is really is

 

[BillyZ]

yay... anyone want 3.9 bags of unused sea salt? might be good for traction I suppose :?

My CA and ALK levels were actualy a little low when I first tested the tank after they started showing poor signs. I used bionic every other day until I got up to the levels I was looking for, so hopefully my alk is actually what i think it is?

if maintained levels of CA and ALK a indicative of "ok" Mg levels, then can you think of another reason my mushrooms may have gown down hill so quickly after looking so good originally?

 

[reefrunner69]

Something about the waterchange disagreed with them. Perhaps an SG shift (personallly I'd bump the SG up to 1.025) or temp swing...ph shift, etc...