PH and nitrites

Discussion in 'Water Chemistry' started by DianeC, 19 Jan 2019.

  1. DianeC

    DianeC Member

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    Just had my cycling tank water tested at LFS as it has been going for about a month. The tank has been cycling for about a month with some plants from my existing tank, biostart liquid and some water from wc from existing tank. The substrate I used is Ocean Free Aquagrow plant and shrimp soil which does state it assists in lowering the pH and KH. On top of that I added a little extra soil about a week ago.
    The result back from the water test showed the nitrites where fine but the pH was 5.25. I was pursuaded to buy JBL Aquadur to help bring up the pH which I will try now.
    I am wondering is the pH due to the newly added soil, will it get better over time and water changes, or is my substrate to low a pH for my tap water chemistry.(hardness level=soft, pH average 8.48)
     
  2. Edvet

    Edvet Global Moderator Staff Member

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    Just do some waterchanges to bring the pH up.
     
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  3. DianeC

    DianeC Member

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    Thanks will do!
     
  4. dw1305

    dw1305 Expert

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    Hi all,
    These work by <"ion exchange">, all the cation exchange sites are initially filled with a H+ ion, which is exchanged for an ion of higher valency in the water. Usually this is a Ca++ ion, because they are usually the commonest multivalent ion in solution.
    They are strange and conflicting numbers, but actually <"quite common now"> because of the sodium hydroxide (NaOH) that they add to soft tap water (to stop lead (Pb) and copper (Cu) from old pipes going into solution).

    This leads to the high pH of the tap water, but it doesn't raise the hardness (either dGH or dKH) because you haven't added any Ca++ or Mg++ or (bi)carbonate (HCO3-) ions to the water. All the Na+ and OH- ions go into solution and there isn't any "buffer" of undissolved salt like there would be if you had naturally hard water (from dissolved limestone CaCO3) with a high pH.

    You can add some carbonate buffering by adding a small amount of calcium carbonate to your tank, <"oyster shell chick grit"> is the cheapest option (you can <"get it at Wilkos">), or you can use one of the re-mineralising mixes from <"James' Planted Tank">.

    cheer Darrel
     
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  5. DianeC

    DianeC Member

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    Thanks Darrel, I must confess its been a very long time since I did chemistry so I'm still working through your reply. The ph and hardness readings came from the water suppliers website for my supply, nothing to do with me working it out!
     

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