High Fluctuations in Magnesium Level

[FSOL]

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

 

[bertoni]

That seems very odd to me. I haven't seen that much Mg consumption reported. Which Mg test kit are you using? What about the other water parameters?

 

[FSOL]

I'm using Salifert's test kit. Calcium is around 320, alk is 10dkh. So far the only valid explanation I've heard from the LFS was that it's a new tank, it's using lots of Mg to build coraline algae on the rocks, and therefore consuming lots of Mg. he said it'll slowly stabilize and stay constant.

 

[bertoni]

I'm not sure I believe that, but calcium should be around 400-450 ppm. That might be an issue.

 

[FSOL]

oops sorry, I meant calcium is 420ppm not 320

 

[Randy Holmes-Farley]

I've also not heard of magnesium dropping so much. I also don't buy the new tank thing as coralline usually grows faster in established tanks.

That said, is there a lot of coralline growth?

How long have you monitored the magnesium?

Are you doing water changes? If so, what is the magnesium in the new water?

What are you adding, and how much?

how are you supplementing calcium and alkalinity? How much?


These articles may be useful:

Magnesium
http://www.advancedaquarist.com/issues/oct2003/chem.htm

Magnesium and Strontium in Limewater
http://www.advancedaquarist.com/issues/dec2003/chem.htm

 

[FSOL]

There is veryyyy slow coraline growth.

I have been monitoring for a month now.

I do 10-15% water change on average every 10-14 days.

I used to use catalina ocean water for changes which had low magnesium levels. Now I use Tropic Marine Pro Reef salt mix. BUT the thing is that even w/ that salt, when I mix it up, the Mg. concentration is around 1100ppm. People told me that's the best mix and has high Mg. in it. I mix it based on the directions and it only gets 1100ppm Mg.

I use Salifert Mg powder to raise my Mg concentration in the tank, and as far as calcium and alk, I use kalk drip. Ca is 420ish, alk is around 10dkh.

 

[Randy Holmes-Farley]

I do not know why your magnesium is dropping so much, unless it is a kit error.

You might try my DIY two part system that should keep calcium, alkalinity, and most important here, magnesium constant aside from drops due to water changes:

An Improved Do-it-Yourself Two-Part Calcium and Alkalinity Supplement System
http://reefkeeping.com/issues/2006-02/rhf/index.php