About Magnesium

Discussion in 'Aquarium Fert Dosing' started by flygja, 18 Aug 2009.

  1. flygja

    flygja Member

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    Penang, Malaysia
    I've been trying to find out what is Magnesium needed for in a planted tank, besides raising the GH. If my GH is high enough, do I still need to add MgSO4 to my EI solution? Thanks.
     
  2. ceg4048

    ceg4048 Expert/Global Moderator Staff Member

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    Location:
    Chicago, USA
    Hi,
    GH just for the sake of GH is irrelevant. GH is a direct measurement of the waters content of Ca and Mg.
    Although Magnesium makes up only about 0.2-0.5% of a plants dry mass, it plays a critical role in photosynthesis. That's because the chlorophyll molecule is constructed of a Carbon/Nitrogen matrix surrounding a central Magnesium atom. So right off the bat, poor levels of Mg will have an immediate negative effect on chlorophyll availability/efficiency and on subsequent sugar production.

    Mg is also critical to the synthesis of proteins, fats, vitamins and carbohydrates. Mg is a catalyst in the transportation of Phosphate as well as in the use of PO4 in energy storage reactions. These reactions, which are quite common and essential, are referred to as Phosphorylation reactions. Chemical energy in a plant is stored when PO4 ions are bonded to other molecules, and conversely, energy is consumed when the PO4 bond to that molecule is severed.

    Mg is also required in the synthesis of DNA/RNA. Mg is also an "activator" of many critical enzymes, particularly those enzymes that are related to carbohydrate metabolism as well as the recycling of some of the waste products of metabolism.

    Because of these functions that Mg participates in, a shortage of this element will have far ranging effects. Lower Mg will result in less Chlorophyll. Since the Chlorophyll pigment has a green color, the leaves of a green plant, (particularly the new leaves) will tend to lose their green and to be more yellowish or pale. This would be less obvious on a red plant though. Less Chlorophyll means less food production, so growths rates would suffer. Remember though, that these symptoms are not exclusive to Mg deficiency. There are a lot of different problems that will have an effect on leaf color and growth rates.

    Since GH of water consists of both Ca and Mg it is necessary to test for at least one of these and then subtract the test result from the GH value to determine the content of the other. It has been demonstrated by JamesC that it is possible to have water high in GH and at the same time low in Mg (high in Ca). The best method if you don't want to test is to add Mg via Epsom Salts (MgSO4) and to slowly reduce the amounts in order to see if there are any negative results.

    Here are a couple of views of the structure of Chlorophyll-a. These pigment molecules are arranged in pairs with their heads (the yellow ring) side by side. This collection of pigments and proteins is called The P680 Complex. The number 680 refers to the longest wavelength of light that the molecules will resonate to - 680 nanometres (Red).
    The area marked in red is the area in which the action takes place. You can see at the center of the ring of "Ns" sits the Mg ion. The presence of this metal within the zone gives the characteristic of very loosely bound electrons circulating in that zone. When struck by light the molecule resonates, causing one of those loosely bound electrons to absorb the resonance energy and to be ejected
    IMAGE_ChlorophyllStructureWithON-small.png

    Here is an iconic view of the molecule showing the orientation of head and tail. Mg is represented by the purple ball. Nitrogen are the blue and Oxygen the Red. Hydrogen are the small cyan balls and Carbon are the grey.
    Chlorophyll2.jpg

    Cheers,
     
    Last edited: 27 Feb 2014
  3. flygja

    flygja Member

    Messages:
    1,270
    Location:
    Penang, Malaysia
    *sweeps brain matter off the floor*

    Thanks for the explanation as usual! Guess I will continue to dose MgSO4 since its not expensive and is quite easy to come by. I'm doing 3-week cycles of EI now, trying to tune the solution as I see fit.
     
  4. chris1004

    chris1004 Member

    Messages:
    565
    Hi Clive, your the man!!!!! Just dropped another information bomb......

    This snippett of info couldn't have come at a better time as its exactly what I've been looking for of late. What sort of quantities of mgso4 would you expect to be taken up weekly in a high tech planted tank?

    I know thats like asking how longs a piece of string and I'm aware of the EI recomendations of 10ppm as a maximum uptake to be supplied. But if mg alters the gh of the tank more specifically the ratio between ca and mg then whats the best and most accurate way to try and maintain this balance of ratio between the two?

    Regards Chris.
     
  5. ceg4048

    ceg4048 Expert/Global Moderator Staff Member

    Messages:
    8,935
    Location:
    Chicago, USA
    Hi Chris,
    Well the first thing you need to do, especially when dosing EI, is to forget about ratios because they are meaningless. As long as you provide unlimited quantities then the plant takes what it needs of each element. Let the uptake ratios fall where they may. I mean, even if ratios were important, you know that if you have 20 different plants in your tank, there would be 20 different optimal ratios because each species would have it's own unique requirement (although there is certain to be a range if this is the case). So there is no way you could satisfy every plant. You can only have one ratio in the tank at any one time. Ratios only become relevant when there is a starvation issue. Why is this? Because plants operate with many internal systems of "checks and balances". Here's an example:

    A production center fabricates a chemical for some specific purpose. But that production center has to be told when to stop production, otherwise it's product, in excessive amounts, can become toxic. To balance this, a second production center produces a different chemical which either neutralizes the first chemical or sends a signal to the first production center to lower it's production. Now, imagine that Calcium is involved in the first product and that Magnesium is involved in the second. Can you see that as long as the plant has access to unlimited quantities of Ca and Mg it can self regulate, so it can produce enough of each chemical to balance production? The plant itself will determine what ratios are important internally.

    Now, using this example lets say there is a severe Mg shortfall. It's not hard to see that if there is insufficient production of the Mg based chemical, it will have trouble mediating or communicating to the Ca based production center, so there may be toxicity issues from an out of control Ca based chemical. This is why the ratio lovers assume that lowering Ca dosing in this case would be the best response.

    This is the power and the genius of EI. All these issues disappear under unlimited availability. As long as there are no shortfalls there is no need to think about what ratio of this to that is needed. Ratios are internally regulated.

    A lot of data about ratios come from studies in terrestrial plants which does not always translate to aquatics. Another thing that people forget is that just because you dose at a given ratio, it does not mean that the plant can uptake at that ratio. Uptake pathways are different, and operate at different speeds. What do I mean by "uptake pathway"? Well there are two basic ways that a leaf uptakes a nutrient. The submerged leaf tissue is analogous to a gas permeable contact lens. It's flaccid and aqueous, so if the concentration of a chemical in the water column is higher than it is in the tissue, simple osmotic pressures will force that chemical into the tissue. This is referred to as a "passive" pathway. The other method is for the tissue to be populated with specific ions that attract the charged particles of interest in the water column. This is an "active" pathway. The way that a chemical travels in soil may differ than the way it travels in the water column, so even here, there would be a difference in required ratios between sediment and water column. The fact of the matter is that, apart from the basic functions like cell structure and osmoregulation, different plants use Ca in different ways. Many use Ca as a signalling system. Others uses Ca to increase the efficiency of NO3 and other nutrient uptake.

    Trying to manage ratios therefore is futile and self-delusional. Those who claim success with ratios have not taken into account that they may in fact be already feeding unlimited quantities of the nutrients involved (since thy have no idea how to accurately measure the quantities available.) So it wouldn't matter what ratio they used because the plants already had what they needed to self-regulate. The EI principle states that if you have an Mg starvation then fix your Mg dosing. If you have a Ca shortfall then fix your Ca dosing. I can guarantee you that if you feed unlimited levels of each, and if you never worry about ratios, you'll never have a problem. :shh:

    Cheers,
     
  6. chris1004

    chris1004 Member

    Messages:
    565
    Hi Clive,

    Thanks for the in depth explanation mate and the time it must have taken you to wright. You know the more I learn about this planted tank game the more fascinated I become by it, can you recommend a descent book for me to read, stuff that, have you written one yet? If not then I think you should and you can put me down for a copy straight away...

    I totally get what your saying but where I was coming from is that I want to stabalise my gh (both ratio wise and level) and yes I'm well aware that you don't worry about that too much either and whats more I know your probably right. Its just that sometimes I seem to get a little bit autistic about tank parameters and can't seem to help myself. :lol: :lol:

    Regards, Chris.
     
  7. aaronnorth

    aaronnorth Member

    Messages:
    3,955
    Location:
    worksop, nottinghamshire
    Dina Walstad "ecology of the planted aquarium" is a good read. It has some in depth cienctific topics in it. aprat from that not anything better from what i have heard/ read.

    the best place is UKAPS & the barr report ;)
     
  8. chris1004

    chris1004 Member

    Messages:
    565
    I won't argue with you there mate. I've been singing this websites praises in every plant related conversation i've been having in the fish shops. I still can't believe how misinformed so many people who really should know better are.

    Will definatly try to get hold of the book you recomended or put it on my christmas wish list. LOl. ;)

    Regards, Chris.
     
  9. aaronnorth

    aaronnorth Member

    Messages:
    3,955
    Location:
    worksop, nottinghamshire
    keep checking forums for the best deals, i managed to pick one up for £12 delivered and it was in mint condition :thumbup:
     

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