Magnesium Usage in Tank

FSOL

New member
Hi everyone,

Does magnesium usage in a reeftank decrease as the tank matures? Right now I lose about 30-50ppm Mg. per day and have to add magnesium to the tank every other day to keep it around 1350ppm. The tank is only 2 months old and I still have a lot of LR that's not covered w/ coraline algae.

I was wondering if as time goes on I'll have to adjust Mg concentration less. I use up a $50 container of salifert's Mg additive in about 3-4 days :(
 
Is this an established 180g reef? If so, Mg should not fluctuate like that, if ever. Check to see if your test kit is good. Let's see what happens if you don't test for 7 days, without adding any Mg. For me, fluctuating Alk/Ca is unstandable (but that's another story), but not Mg.

I'm not 100% sure, but coral bone only contains ~5% Mg, the rest is basically Ca.

Mg should not go down that much in a day. Mg should be very stable and rarely needs adjustment (depending on your SPS load). I personally just top off the tank with limewater and that is sufficient to keep proper Mg and Ca/alk levels and only noticed Mg dropped by around 75ppm in 6 months with no water changes. I have 10 super healthy clams and a ton of purple tip montis but I lost all the montis (not before giving a bunch to my friend) b/c I didn't change any water for almost 12 months. LOL!

You should post your question at the chemistry forum.

GL
 
The tank is only 2 months old and I only have two SPS, one monti cap, and a few softies/LPS in the tank. Most of the tank is still empty but I have lots of live rock that is slowly getting covered w/ coraline algae.

I'm thinking maybe it's the rocks that are taking all the magnesium and using for coraline algae growth.

I dose kalk as well, but kalk doesn't raise Mg levels, only Ca and alk.
 
Test your kalk water. It contains Mg. I forget how much, but the quantity is small. :)

I hope someone else can chime in. I never personally experienced Mg depleting this fast. If you can do a search for "magnesium" on the chemistry forum, you should find a probable answer. Unfortunately, getting the search function to work is like hitting the lottery. LOL!
 
My tank is going on 15 months in it's current incarnation and is almost 4 years old (counting from the begining)... It's a 180 and I find I have to add mg regularly to keep levels up..

I think it depends on what you keep... I've talked to other local reefers (in our club... WAMAS) and some experience this and others do not...

Dave
 
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