Magnesium question

[graveyardworm]

I recently added a kalk reactor and ACIII. I had low and fluctuating pH problems before which I wanted to correct. My pH would fluctuate between a high of 8.3 in the evning, and a low of 7.9 in the morning. I've been using Randy's Improved two part to for dosing Mg, Ca, and Alk for awhile now, but had trouble getting my Alk over 8.

Since adding the kalk reactor 2 days ago and setting the pH limit on the monitor to 8.45 my alk has gone from 7.9's to 8.8 dkh, and my Mg has gone from 1420 without dosing to 1500+. I tested twice with Salifert kit, first test pegged at over 1500, and second test I got color change with the last drop from the 1ml dropper.

Does Alk, pH and Mg have a relationship which would cause Mg to rise as Alk and pH rise?

BTW my Ca has remained constant through this.

[Boomer]

Your Ca++ may be more stable as more of it may be being used abiotically and biotically.

Does Alk, pH and Mg have a relationship which would cause Mg to rise as Alk and pH rise?


Yes to a dergee. Kask rasies the Alk

Ca(OH)2 ---> Ca++ + 2 (OH)

2OH + CO2 ---> 2 HCO3- ( Alk)

Kalks does have Mg++ and some more than others. It may be that you are just getting more of it.


Randy talks about this here;

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

In some cases, most notably that of limewater (kalkwasser), it is not clear that all of the magnesium present in it actually makes it into aquaria. Magnesium hydroxide may settle from solution prior to addition to the aquarium. Consequently, even though analyses of commercial lime products show fairly large amounts of magnesium (the quicklime that I use would produce a calcium carbonate skeleton with approximately 1.8% magnesium by weight),16 how much makes it into aquaria is likely a complicated function of how much lime is added to how much water, how long it is allowed to settle (if at all), and whether any vinegar is added into the milieu. These issues will be explored experimentally in a future article.

Also a good read;

When Do Calcium and Alkalinity Demand Not Exactly Balance?
http://reefkeeping.com/issues/2004-12/rhf/index.htm

[graveyardworm]

I'm using ESV Calcium hydroxide at the moment, but once that runs out I'll be switching to pickling lime, its ordered already through the local hardware store and I'm not sure of brand.

I knew kalk may have some Mg in it but seems a bit excessive.

Thanks for the links to the articles.