I can’t figure out this magnesium thing!

[kevgib67]

Ok, my magnesium is consistently running low and is currently 1230 mg/l. I’ve been dosing a magnesium supplement as directed (see picture) for over a week. My ICP test performed on 4/12/23 showed my magnesium at1260 mg/l. It was as low as 1130 mg/l in March. I use Fritz RPM that states it salt is at 1300-1400 mg/l. I mixed up a fresh batch at 1.026 at 78 degrees and the magnesium was 1350 mg/l, right where it should be. I do a 12.5% water change weekly. What am I missing? Thanks. Oh, I use Salifert for testing with an expiration date of 2/25.

 

[Lavey29]

Kits are notoriously inaccurate for magnesium. Are you seeing good calcium consumption also? This indicates skeletal growth. Corals primarily use calcium for growth and magnesium to lesser degree. Are you seeing more coralline?

 

[Troylee]

Most likely corraline sucking it up… lol

 

[kevgib67]

Kits are notoriously inaccurate for magnesium. Are you seeing good calcium consumption also? This indicates skeletal growth. Corals primarily use calcium for growth and magnesium to lesser degree. Are you seeing more coralline?

Ya over the last month coralline has been increasing but this has been going on for many months. A fix? I also should have mentioned I am using All for Reef. Ca is mildly low at 380. Also ICP showed the same for magnesium.

 

[Troylee]

Ya over the last month coralline has been increasing but this has been going on for many months. A fix? I also should have mentioned I am using All for Reef. Ca is mildly low at 380. Also ICP showed the same for magnesium.

I top off with kalk and use all for reef.. my alk is stable but calcium runs really high ugh… 540 ish… and my mag I cant keep up! I’m burning through it like crazy but I believe it’s the corraline that’s exploding in my tank… dang it!

 

[Lavey29]

Ya over the last month coralline has been increasing but this has been going on for many months. A fix? I also should have mentioned I am using All for Reef. Ca is mildly low at 380.

But are you seeing skeletal growth along with coralline? I went very rapidly from dosing 10ml calcium daily to 37ml now as the tank and coralline thrive. My magnesium is also affected but to a lesser degree. I don't dose mag daily like alk and cal only weekly for magnesium.

 

[Lavey29]

I top off with kalk and use all for reef.. my alk is stable but calcium runs really high ugh… 540 ish… and my mag I cant keep up! I’m burning through it like crazy but I believe it’s the corraline that’s exploding in my tank… dang it!

Now, I wonder if there is competition between the corals and the coralline for growth. The corals may be better at calcium consumption then the coralline so then the coralline goes after the magnesium for its growth needs.

 

[Troylee]

Now, I wonder if there is competition between the corals and the coralline for growth. The corals may be better at calcium consumption then the coralline so then the coralline goes after the magnesium for its growth needs.

I believe it’s something along those lines..

 

[kevgib67]

But are you seeing skeletal growth along with coralline? I went very rapidly from dosing 10ml calcium daily to 37ml now as the tank and coralline thrive. My magnesium is also affected but to a lesser degree. I don't dose mag daily like alk and cal only weekly for magnesium.

My skeletal growth hasn’t really increased or decreased, slow and steady. I will continue all for reef, magnesium and I do have kalk, I’ll start topping off with. Once magnesium is where I would like it I’ll start backing off and learn how often I need to dose to maintain it. Thanks to both of you.

 

[Randy Holmes-Farley]

I expect test error or low salinity is why magnesium is seemingly low.

Nothing consumes magnesium at a rate higher than 1/10th of the calcium. Long term use of kalkwasser (adding calcium and alk without magnesium) can very slowly decrease magnesium, especially with few or no water changes.

 

[Lavey29]

My skeletal growth hasn’t really increased or decreased, slow and steady. I will continue all for reef, magnesium and I do have kalk, I’ll start topping off with. Once magnesium is where I would like it I’ll start backing off and learn how often I need to dose to maintain it. Thanks to both of you.

Since you only do 12.5% weekly water changes its just possible that magnesium is being used slightly more then your water change replenishes thus a slow and constant decline. I have to dose magnesium weekly to maintain levels. I do 20% water change every 3 weeks with coral pro salt. I think you just need to dose a little once a week to keep it where you want it. I keep mine 1400 to 1450.