Magnesium in tap water

Discussion in 'Aquarium Fert Dosing' started by Aeropars, 26 Jul 2019.

  1. Aeropars

    Aeropars Member

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    Hi guys,

    I was reading an interesting threat on using epson salts as part of the EI regiem and that Gh of tap water may not be a mix of calcium and magnesium.

    So I did some digging on Severn Trent's webpage and found that magnese is 1.1 parts per BILLION. I can't find anything relating to calcium.

    I'm guessing thats not much and therefor I'd need to buffer with epson salts but my question is: What should I be aiming for with this?

    All plants apart from H. Pinnafitida are growing well with the the former starting to shop signs of spots of leafs.I'm wondering if this could be some form of cause.

    Thanks
     
  2. Zeus.

    Zeus. Member

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    H. Pinnafitida can be a tricky one to keep IMO still have yet to master it and had it in my tank over a year :rolleyes: . Hygrophila pinnatifida -very sensitive to lack of kalium in the water worth a read ;)
     
  3. dw1305

    dw1305 Expert

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    Hi all,
    Usually there isn't much magnesium in the water in the UK, <"for geological reasons">.
    Same applies plants just need a little bit, but that is definitely too little.

    Any trace element mix will contain manganese (Mn). You can also get iron chelates with added manganese, I've bought "Chempak sequestered iron" in Wilkos etc. .
    It will be all the dGH, if there isn't a quoted value for calcium Ca. I'd be really surprised if you tap water wasn't "hard" (above 200 mg/L CaCO3).

    cheers Darrel
     
  4. Aeropars

    Aeropars Member

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  5. Aeropars

    Aeropars Member

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    Thanks Darrel. So based on that, is it worth me adding Epson Salts or would my trace mix be enough? I have been adding but i guess by doing so I'm hardening my already hard water. Is that right?
     
  6. dw1305

    dw1305 Expert

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    Hi all,
    Add some, there isn't really a downside.QUOTE="Aeropars, post: 567564, member: 30"]magnese is 1.1 parts per BILLION[/QUOTE]That in manganese (Mn), there should be enough in the trace mix.
    Yes, magnesium is (Mg) and the element in "Epsom Salts" (MgSO4.7H2O) that contributes to dGH. If the water is already hard then it won't meaningfully make it any harder, but it will help your plants grow.

    cheers Darrel
     
  7. Zeus.

    Zeus. Member

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    Six million dollar question and lots to consider, I was chatting with @Tim Harrison who also has hard water like me and im pretty sure he said he has issues with H pin. also!
    Yet to find the sweat spot but thinking of doing a RO/tap water mix in my 50l to see if that helps.

    D Wong 2hr guide usefull IMO

    upload_2019-7-29_17-37-25.png

    My current EI dose as off 20/7/19 is

    upload_2019-7-29_17-39-52.png
     
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  8. micheljq

    micheljq Member

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    In the pages of Mr. Wong (the shown pages), which i read many times. He mentions that tap water has seldom magnesium, no potassium most of the time. Magnesium and potassium are quite important, especially hygrophila can require a lot of them. Calcium is often found in tap water, but best verify. Mine in Quebec, has 30ppm calcium, but very few magnesium, i do add epsom salts.

    Michel.
     
  9. Zeus.

    Zeus. Member

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    mine has quite a bit
    upload_2019-7-29_18-18-48.png

    to quote a wiser man

    so my tap water has 5.4ppm Mg yet I still add another 10ppm Mg - its probably a bit OTT, yet it should do no harm that I'm aware. Plus Epsom Salts cost peanuts

    Hard water is complex from what I understand as there lots of Ionic interactions and the water is alkaline also which messes up which Fe to use also :banghead::banghead::banghead::banghead:.

    with your water only having 30ppm Calcium I suspect your water is relatively soft which should make your life easier IMO so I would add some Epsom salts
     
  10. dw1305

    dw1305 Expert

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    Hi all,
    Yes that is it. @micheljq's water is unlikely to have much magnesium, and may not have any. If you have soft water you are unlikely to have more than trace magnesium levels.

    High levels of calcium (Ca) can interfere with the uptake of both iron (Fe) and magnesium (Mg). Hard water is likely to have <"some magnesium"> in it (my guess would be that <"1 - 5 ppm" is fairly typical>), but in the UK it won't have very much, <"away from NE England">. Most of SE England has tap water <"abstracted"> from <"chalk aquifers">.

    Where you have hard rocks, hills and high rainfall (mainly to the N. and W.) you are going to get soft water from reservoirs (Elan Valley, Lake Vyrnwy, Thirlmere etc.)

    [​IMG]
    I don't see any downside to adding some "Epsom Salts" (~ 10% Mg), you are unlikely to have much magnesium in your water in the UK, it doesn't matter whether you have hard or soft water.

    Hard ground water in the <"Central USA, or around the Mediterranean">, derived <"from dolomite"> will naturally be rich in magnesium, as well as calcium.

    cheers Darrel
     
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  11. Aeropars

    Aeropars Member

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    Is there a way to combat this outside of RO water? I was tempted to give RO a go but then its just another expense.

    Are you saying that magnesium isn't something we get much of over the UK in tap water?
     
  12. dw1305

    dw1305 Expert

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    Hi all,
    Yes, if you are outside of the zone of magnesian limestone aquifers (approximately from<" Nottingham to Durham">) then you are unlikely to have much magnesium in your tap water.
    I've used <"rain-water"> since the 1970's without any problem.

    cheers Darrel
     
  13. jaypeecee

    jaypeecee Member

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    Hi Folks,

    FWIW, magnesium in my tap water ranged from 4.00 - 5.90 mg/l last year. My water supplier is South East Water.

    JPC
     
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  14. dw1305

    dw1305 Expert

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    Hi all,
    They would be the sort of values you'd expect if you have hard water. There is (relatively) quite a lot of magnesium in sea water, so you tend to get a little bit dissolved in water from limestone aquifers (limestones are laid down in tropical seas).

    Problems with plant uptake often occur because of the calcium: magnesium ratio. Basically it is just a numbers game, if you have a very high calcium to magnesium ratio, the ion crossing the cell wall into the plant is almost always a Ca++ ion, not an Mg++ one.

    To get raised magnesium level you need a deposit laid down in an <"evaporite basin"> (like at Droitwich, nr. Epsom, N. America or the Mediterranean) or one with ultramafic rocks from deep in the mantle (like the Lizard peninsula).

    You tend to get even less magnesium in water that comes from reservoirs on Granite (SW England) or Millstone grit (Pennines etc).

    cheers Darrel
     
  15. jameson_uk

    jameson_uk Member

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    This is something that has been going round my head but in specific relation to shrimp.....

    My tap water is relatively hard GH 12/13 and KH 5. I believe this comes from a ground water source nearby. Fish and plants and generally OK but I have always had issues with my cherry shrimp. Now I always hear that these are bullet proof and like hard water but I have had a constant stream of failed molts (I have lost 30+ shrimp and I am down to the last two in this batch).

    I am now cutting my tap with about 1/3 Deionised water which get the GH down to 8 and I am seeing less failed molts but I am still seeing them. I have wondered whether a lack of magnesium is playing a part? I am reluctant to just add more Epsom salts (a little does go in as part of my roll your own all in one mix) as this surely must raise GH and higher GH seemed to be causing the shrimps molting issues.

    If the GH was mainly calcium would I not expect to see you a lot more limescale in my kettle???
     
  16. dw1305

    dw1305 Expert

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    Hi all,
    Do you know why the dGH and dKH differ so much? Usually they would be pretty much the same because the hardness (both dGH & dKH) comes from calcium carbonate (CaCO3).
    I'm not sure. Hopefully some-one else will be able to comment.

    Our tap water is ~18 dGH/dKH and they did fine in that, but I would have added some magnesium as well.
    I think more more magnesium isn't going to do any harm. I might try giving them some more vegetables in their diet, I expect diet is at least as important as the mineral content of the water.
    You would, if you don't get much lime-scale that suggests that there isn't a lot of CaCO3 (as HCO3- and Ca++) in the water. Magnesium carbonate (MgCO3.nH2O) is even less soluble than calcium carbonate, so it would still form white "scale".

    cheers Darrel
     
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  17. jameson_uk

    jameson_uk Member

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    No idea. I remember looking into it when I first setup the tank and assumed it was slightly unusual but never actually thought about the chemistry behind it. South Staffs do list some averages for hardness and plenty of measurements of how this is made up
    View attachment water-hardness-ssw-2018.pdf

    I can't quite figure out whether we come under Barr Beacon or (most likely) Sutton Coldfield as we seem on the border. The numbers look in the same ball park either way.

    The only thing I do know is that the treatment plant I think out water comes from (borehole) had a new ion exchange treatment stage added about 20 years ago which was apparently a first at the time. (There are some articles that are way over my head if you search for Little Hay Ion Exchange). My understanding is that this extra treatment was to reduce nitrate levels (presumably from farm run off). I would have thought this would if anything reduce GH not KH?

    We don't actually get much limescale which now seems odd? The house is coming up for 100 years old and there is no softener or anything installed so now I am more confused as to what is in my water.....

    I have tried all sorts... They always seem to enjoy courgette (which I tend to offer once a week) but I couldn't get them to touch broccoli, kale or spinach (despite numerous attempts). I do out mulberry leaves in which I believe are relatively high in calcium. I also put in the odd one of these (https://www.garnelenhaus.com/glasgarten/mineral-junkie-pearls-50g) which supposedly have all the nutrients a shrimp might need.
     
  18. dw1305

    dw1305 Expert

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    Hi all,
    Interesting, slightly more magnesium (Mg) and less calcium (Ca) than you might expect, and not fully saturated with carbonates.
    The only one that really differs is "Winshill". I had to look up where it is, and it is at Burton-on-Trent so presumably has more input from the magnesian limestone immediately to the N. and E. of Burton.
    Staffs_water_hardness.JPG
    It shouldn't effect the cations that make up the dGH. Originally the ion exchange unit may have used a non-selective anion exchange resin, which would have removed all anions (including HCO3-) and replaced them with a chlorine (Cl-) ion. More recently it definitely would have used a nitrate (NO3-) selective resin.
    That is a strange one, do you have a TDS meter? That would give us a bit more idea, even if it doesn't tells any of the specifics.
    Mine liked Courgette as well.

    cheers Darrel
     
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  19. tiger15

    tiger15 Member

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    I never have the need to dose Mg and Ca, as I use dolomite gravel. Dolomite is CaMg(CO3)2, low in solubility, and unlike calcite or crushed coral, will not turn the water super hard.. It provides the right ratio of Ca and Mg, eliminating the guessing game of dosing each mineral individually. I am not sure why no one mentioned using it.

    The dolomite I use is made for aquarium, not crushed garden dolomite which is dusty and may dissolve too fast.
     

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  20. dw1305

    dw1305 Expert

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    Hi all,
    It is mainly geology. You can get it in the UK, but we don't have <"large quarriable reserves"> of it like you do in the USA. It is a slower release source of calcium (and magnesium) compared to aragonite and (most) calcite limestones.

    I used to buy <"powdered dolomitic limestone"> when I made up my own potting composts, and it is pretty widely used in commercial horticulture. I haven't bought any for a while, but it sells for about £1 per kilogram.

    I think the other reason is just that "Epsom salts" (MgSO4.7H2O), approx. 10% Mg, are both cheap and readily available.

    cheers Darrel
     

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