Magnesium levels won't stay up

[John Snider]

So I'm using reef crystals in my 75 gallon mixed reef tank and I'm having trouble keeping my mag levels above 1250. I've tried dosing aquavitro ions, which brings it up but then drops after a week or so. My Ca is 450 and my dkh is 9 which bumps up with every water change, but typically holds steady. I'm looking for suggestions on how I can keep my mag up. I know ur not suppose to chase numbers but I feel that 1250 or lower is too low. Thoughts....

 

[Ron Reefman]

Mg of 1250 is a bit low, but not 'hair on fire' low.

If Ca and alk are fairly stable, then Mg should be super stable. I dose Ca and alk every couple of days and I only have to dose Mg once ever couple of months. Although I do run my Mg level kind of high at 1400.

A few things to consider. What test kit are you using? When you dose, how high does the Mg level get to and how long does it take to fall back down? And how often do you have to dose Ca and alk (if ever)? How often and how big are your water changes with IO Reef Crystals?

I'm not familiar with the Aquavitro ions you are using, but from what I read, it should be working. Maybe try some other brand of Mg to raise the level? I use a magnesium chloride snow melt product (Dow Mag Flake) and Epson salt to raise mine. I use bulk chemicals because at one point a few years ago I had 4 tanks totaling over 600g of saltwater. Oh, and you pay almost $60 for a gallon of premixed Mg. I paid $20 for a 50 pound bag of Dow Mag Flake which will make a couple of hundred gallons of Mg for my tank.

 

[Randy Holmes-Farley]

Magnesium will never drop more than 1-2 ppm per day, and is about 1/10th if the daily calcium drop. There is no other possibly way for it to drop by itself.

 

[Randy Holmes-Farley]

Any substantially faster drop is either testing error, water changes with a low mag salt mix, or due to drops in salinity.