Jump to content


Photo

Magnesium question


  • Please log in to reply
19 replies to this topic

#1
godfathernikki

godfathernikki

    Nano Reefer

  • Members
  • 421 posts
  • Joined 24 Feb 2008
  • Az

Last week I used tech M to boost my mag up to about 1400ppm, and I've been watching it over the last few days without dosing to get an idea of how much is being used.

On average it looses about 15ppm per day, which means to maintain I need to dose about 8ml of Tech M daily.

My tank has a hammer coral with about 10 heads, a candy cane with 10heads, and a 2inch pagoda frag, and a mix of several zoas and mush's - you can see my tank in my sig.

Does this sound accurate? Is there something other than corals that could cause my mag to drop? The reason I ask is because the dosing amount seems like a lot for a 10gal, and the bottle says I shouldn't dose more than 10ml a day, which my daily dosing at 8ml is pretty close to.

#2
1fishmonger

1fishmonger

    Nano Reefer

  • Members
  • 2,055 posts
  • Joined 08 Sep 2010
With those corals, you don't need to dose Mg. Also - Your tank is so small that weekly water changes should be more than sufficient to replace Mg/Ca/Alk/trace elements.

#3
Deano

Deano

    The 3 eyed monster "RIP"

  • Members
  • 1,485 posts
  • Joined 28 Nov 2006
  • The Land of Oz
This article might help answer your question.

#4
godfathernikki

godfathernikki

    Nano Reefer

  • Members
  • 421 posts
  • Joined 24 Feb 2008
  • Az

With those corals, you don't need to dose Mg. Also - Your tank is so small that weekly water changes should be more than sufficient to replace Mg/Ca/Alk/trace elements.


Thanks, but that doesn't quite answer my question. I'm looking for a cause to the depletion. If you feel that I don't need to dose with these corals, then there must be something out of whack with my system.

With a loss of 15ppm per day I would be out of the safe ranges within a week or two if I don't dose, not to mention the effect it will have on my Ca.

This article might help answer your question.


Thanks for the link, I'm checking it out right now.
*pulls out pipe, puts on reading glasses

#5
Deckoz2302

Deckoz2302

    Stony Reefer

  • Members
  • 6,087 posts
  • Joined 29 Aug 2011
  • Raleigh, North Carolina
Where are your calc and alk levels? How big is your tank? I use about the same -14ppm may a day. Over 7 days is 98ppm. Whoever said just do water changes. This is a drastic change in a week. And a 25% water change would only replace about 24.5ppm...dosing is needed as he is doing

Anything that builds a calcium skeleton uses mag. Including your inverts like snails clams ect. Some macros use mag and also magnesium effects your calcium supersaturation - alk affects this also. What's your other params?

OceanariumProject_zpsdcf024fc.jpg

#6
godfathernikki

godfathernikki

    Nano Reefer

  • Members
  • 421 posts
  • Joined 24 Feb 2008
  • Az
Sorry probably should have listed those right off the bat:

12gal Eclipse (closer to 10gal water volume)

tested last Friday:
amonia-0
nitrite-0
nitrate - under 5ppm
Phos - 0

tested last night:
Ca-420ppm
dKh - 9-9.5 (hard to tell with the api kit)
Mag - 1360

I haven't finished the article yet, but there were a few things that really stood out to me that may point to the cause.

1. Calcareous algae has up to 4.4% Mg in its skeleton, most other corals are in the %0.1-%2 range.
If Halimeda falls into this category, I think it could be a cause.

2. The more Mg you have, the more Mg gets used.
I'm going to let my Mg drop to about 1350-1300 and see if that curbs the depletion any.

3.Just like Deckoz mentioned, lots of things use it, inverts, corals, even fish.

4. Mg supplements are extremely dilute.
This explains why it feels like I'm dumping buckets of the stuff into my tank, when everything else usually only takes a few drops...


Where are your calc and alk levels? How big is your tank? I use about the same -14ppm may a day. Over 7 days is 98ppm. Whoever said just do water changes. This is a drastic change in a week. And a 25% water change would only replace about 24.5ppm...dosing is needed as he is doing

Anything that builds a calcium skeleton uses mag. Including your inverts like snails clams ect. Some macros use mag and also magnesium effects your calcium supersaturation - alk affects this also. What's your other params?


Edited by godfathernikki, 14 March 2012 - 09:25 AM.


#7
acropora1981

acropora1981

    Aquatic Biologist

  • Members
  • 1,198 posts
  • Joined 29 Aug 2009
  • Ontario, Canada
I know this isn't the point of your thread, but I read this :
"dKh - 9-9.5 (hard to tell with the api kit)"

I thought I'd mention to you that if you double the sample size (ie, 10ml instead of 5ml at the white line on the test tube) then you can double the accuracy of the test. Each drop then counts for 1/2 of one unit of dKH.

and yes, if you triple it or quadruple it you can get more and more accurate measure of dKH (if you are so inclined).
"She will be mine, oh yes, she will be mine...."


Posted Image

#8
Deckoz2302

Deckoz2302

    Stony Reefer

  • Members
  • 6,087 posts
  • Joined 29 Aug 2011
  • Raleigh, North Carolina
Your running a lower calcium and alkalinity then the magnesium buffers capable of. Causing mag to be the dominant element. If you were to raise your dkh to the 11-12 range and your calc to the 460-470 range you would notice that calc and carbonate will be used faster and your mag depletion will slow down - strontium has the same effect when its over 11ppm.

Edited by Deckoz2302, 14 March 2012 - 09:32 AM.


OceanariumProject_zpsdcf024fc.jpg

#9
godfathernikki

godfathernikki

    Nano Reefer

  • Members
  • 421 posts
  • Joined 24 Feb 2008
  • Az

I know this isn't the point of your thread, but I read this :
"dKh - 9-9.5 (hard to tell with the api kit)"

I thought I'd mention to you that if you double the sample size (ie, 10ml instead of 5ml at the white line on the test tube) then you can double the accuracy of the test. Each drop then counts for 1/2 of one unit of dKH.

and yes, if you triple it or quadruple it you can get more and more accurate measure of dKH (if you are so inclined).



Ahh, that's a good idea, I'll have to give it a try. Usually I have issues with it turning some random shade of green. I stop when it turns green and add .5 to the number of drops since I know it takes less than another full drop to turn color. This way I'm +-0.5 max from the actual number.

#10
godfathernikki

godfathernikki

    Nano Reefer

  • Members
  • 421 posts
  • Joined 24 Feb 2008
  • Az

Your running a lower calcium and alkalinity then the magnesium buffers capable of. Causing mag to be the dominant element. If you were to raise your dkh to the 11-12 range and your calc to the 460-470 range you would notice that calc and carbonate will be used faster and your mag depletion will slow down - strontium has the same effect when its over 11ppm.


Interesting, I was not aware of this.

So I remember reading somewhere that having higher levels of Ca would lead to faster abiotic precipitation-which means higher doses for alk and ca.

In a smaller tank like mine, would it make more sense to lower Mg than raise ca/alk to minimize the amount of swing in my water params when I dose?

#11
Deckoz2302

Deckoz2302

    Stony Reefer

  • Members
  • 6,087 posts
  • Joined 29 Aug 2011
  • Raleigh, North Carolina

Interesting, I was not aware of this.

So I remember reading somewhere that having higher levels of Ca would lead to faster abiotic precipitation-which means higher doses for alk and ca.

In a smaller tank like mine, would it make more sense to lower Mg than raise ca/alk to minimize the amount of swing in my water params when I dose?


Depends. What are the natural levels of your salt? Also precipitation depends on the levels of carbonate. Magnesium and your PH. These levels determine the supersaturation level of the water and its ability to keep elements binded /saturated vs precipitating out

OceanariumProject_zpsdcf024fc.jpg

#12
godfathernikki

godfathernikki

    Nano Reefer

  • Members
  • 421 posts
  • Joined 24 Feb 2008
  • Az

Depends. What are the natural levels of your salt? Also precipitation depends on the levels of carbonate. Magnesium and your PH. These levels determine the supersaturation level of the water and its ability to keep elements binded /saturated vs precipitating out



Not really sure. I'm using premix from the LFS because it was cheaper than buying ro+salt. I tested ca and ph a few weeks ago, 420ppm and 7.9 respectively (ph was low probably from sitting still in a water jug for a week). Haven't tested for anything else in the lfs water. Ph in the tank is usually around 8.0, and dips about .1-.2 at night.

#13
acropora1981

acropora1981

    Aquatic Biologist

  • Members
  • 1,198 posts
  • Joined 29 Aug 2009
  • Ontario, Canada

Ahh, that's a good idea, I'll have to give it a try. Usually I have issues with it turning some random shade of green. I stop when it turns green and add .5 to the number of drops since I know it takes less than another full drop to turn color. This way I'm +-0.5 max from the actual number.


Thats what I do as well :) Once it starts to turn green, I figure I'm about there, and that its just a tad higher than whatever the number of drops indicated.

It also saves on test kits if you don't bring it all the way to the yellow end point ;)

Edited by acropora1981, 14 March 2012 - 10:44 AM.

"She will be mine, oh yes, she will be mine...."


Posted Image

#14
PinkDamsel

PinkDamsel

    Debutante Reefer

  • Members
  • 621 posts
  • Joined 30 Sep 2009
  • New York City

. . . .I stop when it turns green and add .5 to the number of drops since I know it takes less than another full drop to turn color. . . .

How do you add half a drop?
My girdle is killing me!
What do you MEAN blue damsels don't come in pink?!?!?!?

#15
solefald

solefald

    Nigerian Prince

  • Members
  • 766 posts
  • Joined 16 Jan 2012
  • San Diego, CA
You can drive your Mg to insane levels with no ill effects. I've been dosing with Tech M for 3 weeks to kill bryopsis and got my Mg to 1900+. Everything is fine. People do it all the time.

#16
godfathernikki

godfathernikki

    Nano Reefer

  • Members
  • 421 posts
  • Joined 24 Feb 2008
  • Az

How do you add half a drop?


Not half a drop, I add .5 to dkh.

#17
acropora1981

acropora1981

    Aquatic Biologist

  • Members
  • 1,198 posts
  • Joined 29 Aug 2009
  • Ontario, Canada

How do you add half a drop?


You don't add half a drop lol... you add half a degree of KH to your reading. ie, if you count 9 drops your kh is 9.5 by this method.
"She will be mine, oh yes, she will be mine...."


Posted Image

#18
PinkDamsel

PinkDamsel

    Debutante Reefer

  • Members
  • 621 posts
  • Joined 30 Sep 2009
  • New York City

You don't add half a drop lol... you add half a degree of KH to your reading. ie, if you count 9 drops your kh is 9.5 by this method.

Obviously, I misunderstood "drop", lol. :lol:

Recently had to figure out how to measure 0.10 ml of liquid food to my pico (counted no. of eyedropper drops in a ml then divided by 10). Thought this was another technique to get micro-measures!
My girdle is killing me!
What do you MEAN blue damsels don't come in pink?!?!?!?

#19
godfathernikki

godfathernikki

    Nano Reefer

  • Members
  • 421 posts
  • Joined 24 Feb 2008
  • Az

Obviously, I misunderstood "drop", lol. :lol:

Recently had to figure out how to measure 0.10 ml of liquid food to my pico (counted no. of eyedropper drops in a ml then divided by 10). Thought this was another technique to get micro-measures!



Yea my technique is a long way from a micro-measurement. It's more of a "Eh, close 'nough" method :P

Also I don't know if this will help you or not, but there are syringes out there that can measure that small. I have one in my salifert Mg test that has notches down to .01ml

#20
PinkDamsel

PinkDamsel

    Debutante Reefer

  • Members
  • 621 posts
  • Joined 30 Sep 2009
  • New York City

there are syringes out there that can measure that small. I have one in my salifert Mg test that has notches down to .01ml


I figured they must exist, was just too lazy to search for them. Now that I've figured the no. of drops don't need it anymore. Thank you, though.
My girdle is killing me!
What do you MEAN blue damsels don't come in pink?!?!?!?