Mn : Fe ratio

Discussion in 'Reef Chemistry by Randy Holmes-Farley' started by Tmmste, Apr 3, 2018.

  1. Tmmste

    Tmmste Active Member

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    I wondered if there is any information about the ratio between manganese and iron. I would like to combine the two into one dosing solution.

    I notice Kent and Two Little Fishies designed a product for dosing Mn and Fe together. Maybe there is someone here who has an idea about this?

    I currently dosed a drop of Mn-EDTA containing 9.5 ppb and a few drops of Fe-DPTA/Fe-EDDHA. The Fe-bottle says the solution is combinable with other fertilizers. I assume Mn-EDTA is no exception.

    If I know the right ratio for macro/micro algea growth.. this would really help. I would just need calculate the daily dosage and add a specific amount to my top-off water.

    Hopefully someone has an idea of the desired ppm ratio.
     
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  2. Gareth elliott

    Gareth elliott Read, Tinker, Fail, Learn R2R Supporter R2R Excellence Award Build Thread Contributor NJRC Member

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    I think both are going to be hard to test for.
    Iron in nsw is like 2ppb
    manganese is like 1ppb.
    Ive dosed brightwell iron with out testing. Was .05 ml per 10g 2x a week. Randy has an iron dosing article on here that explains it much better. :)
     
  3. Tmmste

    Tmmste Active Member

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    That is ok. I use an ATS only and it will absorb the iron/manganese anyway. Therefore I like to dose them continuesly (via my ATO). However, in what ratio remains a mystery for me. Probably GHA/Macro algea will absorb it in a specific ratio.. else, manufacturers wouldn't sell it combined I guess. I coudn't find an article which shows the ratio nor did I find it in Randy's articles (or I did not look carefull enough)
     
  4. Gareth elliott

    Gareth elliott Read, Tinker, Fail, Learn R2R Supporter R2R Excellence Award Build Thread Contributor NJRC Member

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    I think the ratio an organism uses of each is going to depend greatly on species and the conditions it is in, lighting, ph etc.

    Fertilizers for most plants the ratio is 3.5 parts Fe: 1 part Mn.

    Green algae is the evolutionary base for all plants if i had to guess a starting point would look at botany, where composition is more widely reported.

    I am assuming a lot of similarities based on form of chlorophyll with that statement, those similarities may not turn out true under experimentation.
     
  5. Randy Holmes-Farley

    Randy Holmes-Farley Reef Chemist Staff Member Team R2R R2R Supporter R2R Excellence Award Article Contributor Expert Contributor

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    In seawater that is not altered due to uptake of these elements (which does not apply to either surface water or very deep water), there is about twice as much Fe as Mn. That changes a lot when they are being used.

    This paper suggests that seaweeds contain a lot more Fe than Mn. Tens to hundreds of times more Fe.

    https://akademiai.com/doi/pdf/10.1007/BF02345918
     
  6. Tmmste

    Tmmste Active Member

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    I googled around and found some information pointing in the same direction. 10x or 100x is a big difference though. I wonder what a rough guideline would be.. x100?[​IMG][​IMG][​IMG]
     
    Big E likes this.
  7. Randy Holmes-Farley

    Randy Holmes-Farley Reef Chemist Staff Member Team R2R R2R Supporter R2R Excellence Award Article Contributor Expert Contributor

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    For iron, at least, a lot may just precipitate anyway, instead of being taken up.
     
  8. Tmmste

    Tmmste Active Member

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    Indeed that is true.. to what extend the EDDHA-bond holds in a marine environment is not known. It should be quite strong though and withstand a higher pH than our aquarium water. I do believe the algae will absorb most of the iron.. if there is an excess building up.. the algae in the display tank will also grow faster. I just need a tiny amount of iron and manganese constantly available for the corals and everything that is excess needs to be consumed by the scrubber. Time will tell.. nice experiment.
     
  9. Tmmste

    Tmmste Active Member

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    So I finally got my anwer nd know the Mn-concentration.

    1 liter contains 80 gr of Mn-EDTA. so 80.000 ppm... 1 drop for my 400l tank is 9.5 ppb. I have added a drop each week.. nothing died. Apart from that I started dosing KNO3.. I noticed my po4 is 0.2 and no3 2.0/3.0.. i overfeed and assumed the scrubber would absorb everything.. appparently not entirely true.. maybe too much denitrification of maybe a lack of no3 due to low fishload is inhibiting algae growth... and maybe when food is broken down instead of eaten.. more po4 is produced? I wonder to what extend this is correct.[​IMG]
     
  10. Big E

    Big E Well-Known Member

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    There is a simpler way to go about things, especially if you plan to keep a dominant Acropora system.

    Get rid of the Algae filter..........it's competing with the corals for those trace metals and nitrates. You probably wouldn't have to dose trace metals like iron,Mn, ect. or nitrates if you did this.

    Either way you touched on one thing that is very important and that's adding more fish.
     
  11. Randy Holmes-Farley

    Randy Holmes-Farley Reef Chemist Staff Member Team R2R R2R Supporter R2R Excellence Award Article Contributor Expert Contributor

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    It is common for reef tanks to have residual phosphate when nitrate is running out, and I think the most likely explanation is denitrification.
     
  12. Tmmste

    Tmmste Active Member

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    I understand Big E. Keeping it simply is why I really want to make this a success. I got rid of the skimmer and mediareactors.. (I want to keep nps without the hassle of dosing from a fridge). Apart from the scrubber, there is nothing.. I'll get there, it just takes some time to finetune the dosed elements. I only have a 400l tank and feel there are enough fish in there.. but I just dump a lot of food in there 'assuming' po4:no3 is created in the same ratio as it is consumed by the scrubber.. but this is not the case. At least, not if the fishload doesn't match the amount of food added to the tank... bacteria are responsible for this apparently.. nitrates does not disappear unless it is transformed into a gass.. like Randy explained. No3 & Po4 will not go below 2.0/1.0 and 0.03 I noticed this some time ago.. the algea will starve and die off before corals do.
     
    Last edited: Apr 11, 2018
  13. Tmmste

    Tmmste Active Member

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    I've been dosing potassium nitrate since last week; no3 inceased to 4+ (out of range of my testkit). It should be around 8. (+ 1.25 ppm each day). To my surpise it did not increase algae growth of the scrubber. I did not expect this to happen... (I am a bit shocked actually). I wonder what is going on here... it just does not make any sense to me.. what am I missing? silicate? copper? zink?.... Sr/K/B/I/Mo/Mn/Fe are all added to the tank... so there must be something the tank is lacking.
     
  14. Randy Holmes-Farley

    Randy Holmes-Farley Reef Chemist Staff Member Team R2R R2R Supporter R2R Excellence Award Article Contributor Expert Contributor

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    A whole host of elements can limit growth if they get too low. I’m sure it cannot be silicate or strontium for algae, but could be lots of different things and dosing them does not necessarily mean they are not still limiting.

    I showed in another thread that a little chaeto can strip the manganese from a lot of seawater.
     
    Last edited: Apr 16, 2018
  15. Big E

    Big E Well-Known Member

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    Randy,

    Can you give me a link to that thread on manganese uptake from chaeto?
     
  16. Randy Holmes-Farley

    Randy Holmes-Farley Reef Chemist Staff Member Team R2R R2R Supporter R2R Excellence Award Article Contributor Expert Contributor

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    Here's a copy and paste of the post:

    From:
    https://akademiai.com/doi/pdf/10.1007/BF02345918

    Chaetomorpha (two species: linum and antennina) had 20-90 ug Mn per g of dry weight. Say an average of 50 ug/g.

    In a 100 gallon aquarium at NSW Mn levels (165 ng/L), there will be 378.5 l X 165 ng/l = 62.5 ug of Mn

    To consume all of that would take 62.5 ug / 50 ug/g = 1.25 g.

    Thus, 1.25 g (dry weight) of Chaeto will take out all of the Mn.

    FWIW, a second paper shows a factor of 5-10 lower Mn in chaeto, but it is still a lot, with 1o grams taking out all the Mn from 100 gallons.
    http://www.nrcresearchpress.com/doi/10.1139/b58-026#.WrpvEYjwYdV
     
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