Raising Mg
 

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???:confused:
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,:smile:

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.

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

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

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.:rolleyes:

Cheers,:smile:

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 :eek:

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.

:eek:

Steve

Actualy it might be the worst way:mrgreen: 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

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.

In past years, before reactors, I always used ESV magnesium with good success. When I started to run a reactor with ARM media, the level was always around 1350ppm.

I dont run a reactor anymore. I now add a magnesium product to any new batch of saltwater. Plus a spoon of calcium, to bring it up to proper levels.

The main tank is 180gal and I estimate the sump has 25gal in it. (EDIT: The sump tank size is 33gal, so instead of calling it 213gal gross I call it 205gal net. Ya, I know. Whatever. Sorry for any confusion this may have caused.) I realize that the LR and LS displaces water and that the 205gal isn't a true net amount, it's just that everyone, for the most part, when speaking of their tank's size refers to them as the size that they are....as if nothing were in it. Unless someone knows a formula for how much water LR/lb displaces I will continue to go with 205gal. There is also a density issue with the LR that complicates figuring that out. Your 95.2/170 works out to 56%...or, looking at it the other way, 44% of your system taken up by LR & LS, etc. I am quite certain that I have more water in my system than 56%.
Also, I need some sort of benchmark and I do not intend to dump all the Mg in at once and then test, but rather I will add and test in intervals. So, hence the 205gal as a benchmark...and yes I agree that I will probably have some left over, but it is not as expensive as some might believe, IMHO. Check out the price of a Kg at J&L. It is actually quite cheap, IMHO.

Cheers,:smile:

Yeah, it's crazy how much Mg I go through, in all three tanks! But I'm getting astounding coralline growth where I had little before, especially in my MH tank. Even my halimeda is prospering.

I go through periods where I pay close attention to the chemistry in my reefs and other periods where I test and adjust alk, Ca and Mg rather infrequently. When dripping kalk nightly, I really notice how low Mg gets and how Ca stays at about 400 ppm. When I don't drip kalk for periods of time, Ca and Mg get low. Alk is always low, whether I drip kalk or not, though it is much, much lower when I don't drip kalk nightly.

I wish the chemistry guy at RC would do a study on how much Mg and how much Ca is required to build stony corals, coralline algae and calciferous algae. We might be surprised with what he finds out.

Bev have you ever checked out your newly mixed salt water for Mg? That seems like a pile of it to go through. I run calcium reactors on my 2 large systems but not on my 44g, 24g or 12g and rarely do I have to suppliment mg. I was using formula salt which tested at about 1200 for mg but am switching to Tropic Marin and Seachem salt which I have not tested newly mixed up water yet.

Ruth,

Am using Kent salt, which I understand may be low in Mg. Haven't tested it, though, after mixing up a batch of NSW.

Also, don't have Ca reactors on any of my tanks. Heck, don't even skim or have sumps. Very low tech operations in our reefs. Rely on hands on work to keep our BB tanks in shape. Should take some pics of them and post to the new thread. They look great. No nuisance algae in any of the tanks. Corals, BTAs and frags are all doing very well :)

I just tested my Kent salt batch for Mg.

I mixed up about 18g @ 78F & 1.025. My Mg was right around 1220ppm. (Salifert) This I imagine would be alittle higher if I was mixing to 1.026

Thanks for sparing me doing the test :biggrin:

So it would appear that my systems utilize a lot of Mg.

I wonder how many people actually test and record Mg levels in their tanks and how much they dose to top up their levels when they test low???

I test for calcium, Alk/hardness and mg. every 2 weeks when I do water changes. If my mg. is a little low I dissolve a couple of heaping tablespoons in a glass of tank water and add it to my sump and then test again and repeat if necessary. All my test kits are Salifert and I replace them every 6 months whether they are used up or not. My 44g cube which has SPS, LPS and softies in it I think I have only had to add mg. once in the last 6 months.

Me, I include Mg in my bi-weekly tests and I correct it then and there if it is below 1350.

Steve

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Good thread! Anyone out there using Epsom salts for Mg supplimentation? It would be by far the cheepest way to do it. Also, I've had this lingering question for a while about ARM media. I don't have a Ca reactor, but would would the effects be of throwing ARM media in a filter bad in my sump?

Read the Mg article. It will tell you why not to use Epsom salts alone to raise Mg.

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Sorry, I wasn't in a reading mood, but your word is good enough for me Bev.:biggrin: