All about Water Hardness

Discussion in 'Water Chemistry' started by JamesC, 16 Feb 2009.

  1. JamesC

    JamesC Member

    Joined:
    3 Jul 2007
    Messages:
    1,276
    Location:
    Bexley, Kent
    Hiya,

    These large osmosis plants are new to me except for when I've been on holiday. The KH you have is fine and it shouldn't matter too much from what it comes from. The GH is more difficult as normally it is made up from Calcium and Magnesium but can also come from any other multivalent cation. I'm not sure what your filtered sea water is going to contain but I'd guess it'd have plenty of calcium. If you are concerned then adding 5ppm magnesium from magnesium sulphate should be fine. A GH of 6 is fine.

    Try it and see how it goes.
    James
     
  2. mzm

    mzm Member

    Joined:
    4 Feb 2010
    Messages:
    160
    Location:
    Malta
    hi james thank you for your advice. I will everything as is and see how it goes.

    Michael
     
  3. jellyfish6

    jellyfish6 Member

    Joined:
    4 Apr 2008
    Messages:
    54
    Location:
    Glos.
    My water authority classes my water as Hard, but then provides 3 water hardness measurements......which should I be using in relation to this article ? Am I correct to say I should be looking at the German hardness?


    Hardness Level Hard
    Hardness Clark 18.00
    Hardness French 26.00
    Hardness German 15.00

    Thanks
     
  4. dw1305

    dw1305 Expert

    Joined:
    7 Apr 2008
    Messages:
    9,203
    Location:
    nr Bath
  5. m_attt

    m_attt Member

    Joined:
    6 Mar 2011
    Messages:
    274
    interesting thread, but i live in a soft water area, but cant find out much on how this changes or effects things.
     
  6. dw1305

    dw1305 Expert

    Joined:
    7 Apr 2008
    Messages:
    9,203
    Location:
    nr Bath
    Hi all,
    It doesn't really, it is much easier to add solutes (salts) to water, so when you add the nutrients your plants need you will naturally add some dGH (the 2+ ions like magnesium (Mg) and calcium (Ca)).

    The "soft" in this case really refers to the temporary or carbonate hardness (dKH), theoretically lack of carbonate hardness (as bicarbonate ions HCO3-) can effect biological filtration. This is because the nitrification of ammonia (NH3 as NH4+) utilises both oxygen (O2) and carbonates (HCO3 in solution, CO3 as a buffer).

    To balance the equation you get:
    Which approximates to 4.3mg O2 & 8.6mg of HCO3- are consumed for every 1mg NH3 oxidised to NO3.

    I say theoretically, because in the planted tank this isn't really that relevant and potentially you can have very low dKH values. Soft water gives you the potential to grow plants like Tonina, that doesn't do well in harder water, and to keep black water fish, see the excellent "Joe's Tank" <http://www.ukaps.org/forum/viewtopic.php?f=27&t=16361&p=184861&hilit=Dicrossus#p184861>. Some other plants don't do well in carbonate depleted water, Vallisneria comes to mind, although I believe that if you use added CO2 and EI this isn't necessarily true.

    The other thing you need to take into account is the carbonate <-> CO2 equilibrium:
    You can alter this equilibrium by adding CO2 or the other way by adding carbonate (disassociated as HCO3-) ions, and this is the buffering we measure as dKH. Details here: <http://en.wikipedia.org/wiki/Calcium_carbonate#Solubility>

    This is the reason people who add CO2 usually buffer their tank water up to 4dKH. You can do this in a number of ways: (from the excellent James' Planted Tank <http://www.theplantedtank.co.uk/RO.htm>)
    From the same link it gives you a fertiliser calculator and an RO re-mineralising mix that you could use for your soft water.

    Cheers Darrel
     
  7. heliwilly

    heliwilly Newly Registered

    Joined:
    23 Feb 2012
    Messages:
    7
    I am about to set up a planted tank, and would like to find out which water chemistry test kit will give me the most accurate results. I have looked at Hagen, API, Colombo Aquatest, and the Kusuri/Palintest kits. What tests are others using and having success with? The tank has JBLAquabasis plus substrate, topped with JBL Manado, it will have CO2 as well via a ladder Bubble counter/Diffuser. Is a CO2 test kit useful or is the normal Bromethyl Blue checker sufficient? Any suggestions would be welcome. I am also trying to get a tapwater report from the local water supplier to Hull, which is Yorkshire water. Cheers Bill W
     
  8. darren636

    darren636 Member

    Joined:
    5 Aug 2011
    Messages:
    1,913
    Location:
    dorset
    if you are setting up , i would buy the api master kit. Cheap and ok for the job. A drop checker is the default method of measuring co2 in a tank. Takes a while to get used to but now i find it essential.i imagine your water will be soft. Just check your kettle for limescale
     
  9. ian_m

    ian_m Global Moderator Staff Member

    Joined:
    25 Jan 2012
    Messages:
    5,106
    Location:
    Eastleigh
    As many people would say, don't bother with test kits, just use your drop checker to get an idea of you CO2 levels.

    I got my water hardness figures (very very hard for Eastleigh Hampshire, 20 Clarke) by phoning up the water board and asking. Also just found it on Southern Waters website for me, confirming 20 Clarke, 300mg CaCO3/l). Also I took a sample of water to my local fish shop (Maidenhead Aquatics in my case) and getting them to test the water, which in fact is the same as mine, all supplied from chalk borehole at Twyford.
     
  10. Martin63

    Martin63 Newly Registered

    Joined:
    1 Nov 2016
    Messages:
    1
    Location:
    Tonbridge
    Interesting article James.
    Maybe I'm nitpicking but you say "To raise KH you can add calcium or magnesium bicarbonate", which gives the impression people could buy these bicarbonates (which don't actually exist as solids). Maybe simpler to say that under normal circumstances KH can simply be restored using an appropriate mix of dechlorinated tap water (which already contains these bicarbonates) and pure water.
    Very good use of references.
     
  11. dw1305

    dw1305 Expert

    Joined:
    7 Apr 2008
    Messages:
    9,203
    Location:
    nr Bath
    Hi all,
    Unfortunately "JamesC" is no longer a member of the forum.
    No they don't, the HCO3- ion only exists in solution as one of the forms of TIC in a carbonate buffered system.

    co2_hco3-png-1550-png.88321.png
    I think this is what we recommend for people who have a hard tap supply. I use rain-water in the tanks, and I buffer it if necessary with our tap water. I'm lucky that I have tap water from a deep limestone aquifer and about ~17dKH, other members (particularly in the S. and E. of the UK) will have a tap supply of lesser quality.

    Members who live in the N. or W. of the UK may find they have an alkaline tap supply, but one where the alkalinity is from added sodium hydroxide (NaOH), rather than carbonates, in which case they will need to add a source of carbonates via calcium carbonate (CaCO3) or potassium (bi)carbonate (K2CO3/KHCO3).

    Sodium carbonate/bicarbonate (Na2CO3/NaHCO3) isn't recommended for the planted tank.

    cheers Darrel
     
  12. JMorgan

    JMorgan Member

    Joined:
    18 Oct 2015
    Messages:
    108
    Location:
    North Yorks UK
    I've just read through this thread for the umpteenth time (over the last year and more) and I think (I use the word very loosely) I might be beginning to grasp the bare essentials at last.

    I've read in several threads that Sodium compounds aren't desirable in planted tanks - but if water companies are using so much NaOH to increase alkalinity to avoid the metal corroding properties of what would otherwise be very soft acid water, what impact does this Sodium have on the planted tank?

    I was trying to (inexpertly) help someone who has what they described as very soft water but with a pH above 8.5 out of the tap. I assume this must be a classic case of NaOH being added? What happens to this water over time in the aquarium or a water reservoir? Is the alkalinity stable? Would such water have a low conductivity and a high pH? If the conductivity is that low, is the pH value even meaningful since its a ratio rather than a measurement?

    I'm not sure I'm asking the right questions here, it just seems to me that since the practice of adding NaOH is now so commonplace in certain areas, it would be good to have a better grasp of how it impacts on the aquarium and what if anything needs to be addressed? And also that this might be very useful in a thread that's "All about water hardness"

    thanks
     
  13. dw1305

    dw1305 Expert

    Joined:
    7 Apr 2008
    Messages:
    9,203
    Location:
    nr Bath
    Hi all,
    It is only a small amount of NaOH. Sodium hydroxide is a <"strong base"> ("caustic soda") which means that you can add a small volume of it to a large volume of water and still raise the pH.

    I assume that the water companies use NaOH because you get maximum "bang for your buck".
    Almost certainly the high pH is because of the NaOH added during treatment.

    What happens in the aquarium would depend on how many acids "proton donors" you have. A proton (H+) will combine with an OH- to give you H2O (theoretically ~pH7). All sodium (Na) compounds are soluble, so the Na+ ions will just remain in solution.
    All the Na+ and OH- ions are in solution. This means that you have no reserve of undissolved alkalinity ("buffering") and as soon as the OH- ions are neutralised (H+ + OH- = H2O = pH7) then any addition of acids (H+ ions) will cause the pH to fall, because there are no CO3, or OH- ions, to neutralise them.
    Yes, I would expect the conductivity to be fairly low (they haven't added many Na+ or OH- ions).
    Yes, so the high pH is a bit of a red herring. I've tried explaining to people, <"on other forums">, about the difference between carbonate buffered alkaline water and water where the pH is high, but without any buffering, not always successfully.
    Probably would be useful.

    cheers Darrel
     
    Last edited: 24 Feb 2017
    xim and JMorgan like this.
  14. dw1305

    dw1305 Expert

    Joined:
    7 Apr 2008
    Messages:
    9,203
    Location:
    nr Bath
    Hi all,
    I should have said that I couldn't find much about the technical details of NaOH treatment in the UK.

    A couple of reports from water companies mention building "sodium hydroxide" dosing plants. This is a fairly short one from <"Welsh Water">.
    cheers Darrel
     
    JMorgan likes this.

Share This Page

Facebook Page
Twitter Page
  1. This site uses cookies to help personalise content, tailor your experience and to keep you logged in if you register.
    By continuing to use this site, you are consenting to our use of cookies.
    Dismiss Notice