Raising Magnesium

Fringe09 · Nov 30, 2017

Hi fellow reefers. Another newbie question.

I am dosing Calcium & Alkalinity using the Neptune's two part doser. ESV B-Ionic.

Question on Magnesium. When the time comes that I need to raise it, does it need to be dosed via a doser in small increments like Calcium & Alkalinity?

JimWelsh · Nov 30, 2017

No, within reason.

Randy Holmes-Farley · Dec 1, 2017

As Jim points out so succinctly

, magnesium depletes very slowly. It might deplete 1 or 2 ppm per day (which is about 0.1% per day) while alkalinity can deplete 10-40% per day and calcium by 2-4% per day.

So on a percentage basis, the magnesium depletion and dosing is much less. If you manually dose a weeks worth of magnesium at once it is not typically a concern, while waiting a week for calcium is undesirable and for alkalinity it would often be a disaster in a high demand tank.

Fringe09 · Dec 1, 2017

Thank you both.

Jason_1990 · Dec 1, 2017

I have a reading of 1020 magnesium. 40 gallon volume water says I'd need
416 ml I could dose that over a Week?

Randy Holmes-Farley · Dec 1, 2017

Jason_1990 said:
I have a reading of 1020 magnesium. 40 gallon volume water says I'd need
416 ml I could dose that over a Week?

I saw that in another thread, but didn't comment. I'd definitely double check that it is accurate with a different kit since it would be unusual for magnesium to get that low, but not unusual for a test results to give an inaccurate reading.

What kit?

What salt mix and salinity?

Jason_1990 · Dec 1, 2017

I'm unsure. My lfs tested it an said that it was very weird also. Couple things could of caused it. I'm pretty sure I spiked my alkalinity using a ph buffer. 2nd I've had a green star polyp in the tank Sence week 2 an have only done one water change last week. Tank had been up 6 weeks.

Randy Holmes-Farley · Dec 1, 2017

None of those things will lower magnesium enough to notice.

What salt mix?

In a new tank, magnesium will exactly reflect what is in the salt mix, and unless it is a bad batch (unlikely) or the salinity is quite low (possible), magnesium is fine.