Raising Mg

Johnny Reefer · #1 01-28-2006, 04:40 AM

Just lookin' for opinions on this.
I'm using SeaChem Advantage Mg to raise my Mg from 975 to 1,290.
The jar says that 5 grams will raise 21 gallons by 5ppm.
My system is 205 gal net.
205/21=9.76. Right?
9.76 x 5g= 48.8grams. Right?
1,290ppm - 975 ppm = 315ppm. Right?
315ppm/5ppm = 63. Right?
63 x 48.8grams = 3,075 grams. Right?
This seems like a whole whack o' Mg to me.
I have to dose over 3 Kg's of Mg to get up to 1,290ppm???

Does this sound right?
Anyone else ever have to use so much Mg, initially?
(Seems like I'm gettin' a calculation wrong here?).

Thanx much,

Ruth · #2 01-28-2006, 11:47 AM

Heya Mark I use the Seachem stuff as well but don't bother going through all the calculation like you do. I know that you do have to use quite a bit though when you are raising it that much. What I do is mix about 3 tblsp. at a time in some tank water to dissolve and then add it to my sump. Test the next day - see where I am at as far as mg. level goes and just keep repeating the process every day until I am at where I want to be. I have never had to raise it that much but to raise it even 100 points takes me about a week to do. I find that this is a good way to monitor and not go too quickly. Besides with a bunch of live rock in there I am never sure of what my exact water volume is.

Beverly · #3 01-28-2006, 01:38 PM

Mark, when measuring the size of your tank, measure the inside of your tank, not the outside. Makes a big difference sometimes in the total volume. Then use the Aquarium System Volume Calculator to calculate real volume. I think the calculator adjusts for rock volume as well. There is also a place to add in the volume of your sump:

http://home.comcast.net/~jdieck1/volcalc.html

Once you have the right volume, use the Reef Chemistry Calculator to double check your calculations. I don't use Seachem products, but Seachem's Mg products are listed in this calculator. When my Mg gets low, but never as low as your levels, I have to add a whole whack of of Kent's product:

http://home.comcast.net/~jdieck1/chem_calc3.html

StirCrazy · #4 01-28-2006, 04:00 PM

Quote:

Originally Posted by Johnny Reefer

Just lookin' for opinions on this.
I'm using SeaChem Advantage Mg to raise my Mg from 975 to 1,290.
The jar says that 5 grams will raise 21 gallons by 5ppm.
My system is 205 gal net.
205/21=9.76. Right?
9.76 x 5g= 48.8grams. Right?
1,290ppm - 975 ppm = 315ppm. Right?
315ppm/5ppm = 63. Right?
63 x 48.8grams = 3,075 grams. Right?
This seems like a whole whack o' Mg to me.
I have to dose over 3 Kg's of Mg to get up to 1,290ppm???

Does this sound right?
Anyone else ever have to use so much Mg, initially?
(Seems like I'm gettin' a calculation wrong here?).

Thanx much,

nope sounds close. what you should do is take some warm RO water and dissolve say 1 cup of the reef advantage in it (this is the same stuff I use) then add that to your sump. the next morning measure your Mg and see how much it increased. Now you really got to look at it and ask do you really have 208 gal of water in your tank, how much does the rock displace ect...
I do this test with 1/2 a cup but you should have at least twice the volume of water as me so it will be better with 1 cup. and I will tell you it takes a lot to bring it back up but then you will hardly use any for a long time.

I should also note I raise my Mg by 100 ppm per day approximately and have never had a problem with anything at this rate.

Steve

Johnny Reefer · #5 01-28-2006, 04:27 PM

Thanx guys.
And thanx for the chemistry calculator Bev. It confirmed that I calculated correctly, (although not a week ago), and I need to go out and buy another 2 Kg's of the stuff.

Cheers,

Beverly · #6 01-28-2006, 06:13 PM

Mark,

Buy lots extra. Depending on the uptake of Mg in your particular tank and its inhabitants, you should be dosing it weekly to keep it at about 1300 - 1325 ppm. I go through three or four times as much Mg supplement as I do Ca, and I drip kalk nightly in our three tanks to help keep up the Ca and alk

untamed · #7 01-29-2006, 05:31 AM

Yes...it is difficult to move Mg a lot upward if you've gotten too low. In fact, the best way to move it might be to do significant volume water change.

...because as you've correctly identified...it takes a ton of Mg supplement to correct your Mg level.

StirCrazy · #8 01-29-2006, 06:01 AM

Quote:

Originally Posted by Beverly

Mark,

I go through three or four times as much Mg supplement as I do Ca,

Steve

StirCrazy · #9 01-29-2006, 06:07 AM

Quote:

Originally Posted by untamed

In fact, the best way to move it might be to do significant volume water change.

Actualy it might be the worst way

salt mixes are almost all low for Mg content. I have tested two popular types now and while they are not overly low they are under 1100 in a fresh mix.

there was a big thing on this a couple years back and it has to do with the cost of the Mg additive and how much is needed.

Johnny Reefer, how are you calculating that you have that much water? like I mentioned befor you have to take off the amount of rock/sane/ect you have or you will be buying way more Mg additive than you will need. I have a 170 gal setup with the tanks, but when I did my calculations on how much Mg attitive I used to how many PPM it went up in my tank it worked out that I only have 95.2 gal of actual water in the system. this is a nice thing to do if for no other reason than to figure out exactly how much water you have for future additions of different attitives. takes the guess work out of the picture.

Steve

Ruth · #10 01-29-2006, 01:37 PM

I have just started to switch one of my tanks over to the new Seachem reef salt which is supposed to be higher in Mg. - I will test it next week when I mix up a batch. The other thing I have heard of but have never tried is to run some - I believe it is dolomite - in your calcium reactor to maintain mg.