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Thread: Calcium, Potassium and Magnesium

  1. #1
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    Calcium, Potassium and Magnesium

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    I read in a newsgroup archive about Ca uptake by plants being inhibited by excess K and Mg. And that the plant will show Ca deficiency.

    Is there truth in this? I am not sure if I am experiencing this in my tank. I dosed weekly with Mg and K, probably a little excessive. And some of my plants (Gratiola, Star Grass) show dying new shoots and fragile new leaves. My Sword plant start having holes in the leaves but leaving the veins -- starting to look like the Madagascar Lace plant!
    koah fong
    Juggler's tanks

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    I think if ca shortage, you can check for KH.

    if your KH above zero ,then that's not it

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    not necessarily

    kH is CARBONATE hardness
    no real correlation with calcium in our tanks
    many people dose with sodium bicarbonate to increase kH

    gH is general hardness
    both ca2+ and mg2+
    but if he's dosing magnesium and potassium then it's a bit LPPL cos you'll never know it's calcium or magnesium

    sera sells ca2+ test kits
    not sure if it works for freshwater plants

    anyway, kf, gratiola isn't sensitive to K and Mg
    i had so much potassium and magnesium (<- this from seachem equilibrium, cheap and good, easy to get (petmart), imo replacement for liquid K/Mg supplements) and the plant was flowering like mad, emersed growth

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    Thanks.

    Right now I will try to add K but not Mg. See how it goes from here. Anyway I happen to have crush coral in my tank - so I believe they are a source of Mg and Ca too.
    koah fong
    Juggler's tanks

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    Ca deficiency is very obvious. You should see deformed leaves, usually in fast growing stem plants like MM first.
    Holes in leaves is Potassium deficiency.
    Dying leaves can be Fe...
    What concentration of Mg are we talking about?

    KH not = to GH. KH does not tell you how much Ca you have in water. They exist independent of each other.

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    CK:

    For many months I have been adding 20ppm K and 5ppm Mg per week after water change. I used to see pin-holes in my Sword plants before but this time they develop such a big hole. My 4ft tank has about 2/3 of crush coral. The other fertiliser I used is Dr Mallick's trace element solution. The ingredients doesn't state Ca.
    koah fong
    Juggler's tanks

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    I have tested the GH of my tap water. It is about 3°GH. If you can test the GH of your tank, you should get a rough idea of amount of Mg2+ and Ca2+ in your tank taking into account of the Mg2+ you added.

    If I am not wrong, Sera Ca test kit is for Marine aquriums where the range is about 300+ to 400+ppm. Not suitable.

    I add about the same K+ as you. Maybe you can reduce it by half to see the reaction. I did see same phenomena on my Hygorphila once... but did not link it to excess K. I added Seachem Equilibrium instead. Maybe I should check too.

    BC

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    Your levels of K and Mg are with in a very safe range. I thought you are dosing a few g/l of Mg or something. regarding the holes in the leaves, maybe something is eating them? Clown loach comes immediately to mind.
    IMO, no need to lower K, if anything, increase it.
    It is hard to put a finger on plant deficiency by just looking at the plant symptoms....

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    Hmm... my swordtails also like to bite a few holes in my plants.

    BC

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