A real confusing matter of KH water chemistry...

Discussion in 'Water Chemistry' started by Aeropars, 30 Jul 2007.

  1. Aeropars

    Aeropars Member

    Messages:
    779
    Location:
    Leicester
    Hi Guys,

    I've been curious about this for some time and really dont understand whats going on.

    So.. here is whats in the tank:

    Tropica plant substrate
    Seachem Onyx Sand
    Redmoor Wood
    Dragon rock

    A test of the tank water on the first attempt took 26 drops of a Nutrafin testkit. Thats 14.5 kh.

    Next I test the tap water straight out the tap... that comes out at 10 drops which is 5.7kh

    I go back to the tank and then get a 21 drops kh of 11.7

    I understand that on the first test of the tank the test tube could have had some residule salts from drying naturally so that probably explains the slight increase in kh there.

    But what the hell has raised my tank KH by nearly 10kh if the tap water is 6 at most?

    I've been wondering about this for some time and i initially thought I had harder water out the tap but havent tested this for bout a year so perhaps somethings changed on that front.

    Can anyone she some light on this?

    Lee
     
  2. Ed Seeley

    Ed Seeley Member

    Messages:
    3,262
    Location:
    Nottingham
    Well as far as I can see it Lee there are four options.

    The first is that the tesat kits are giving you false readings. For there to be difference of nearly 3dKH between test on the same water seems a little dodgy to me. But then both test on the tank were higher than the tap water.

    If they are 'real' readings then the obvious one is that part of the decor is calcerous and is raising the KH. What's the dragon stone and is there any calcerous material in the sand? Or even does the Tropica substrate up KH? You could test all of these in a jar with tap water and see if they up the KH there.

    The second one is evaporation. I don't much about your tank, but if it's an open tank it could have very high evaporation and if that evaporation's replaced with tap water then you're upping the TDS all the time. 10dKH would be pretty high accumulation though and water changes should quickly dilute it back to more normal levels.

    The third option is that some plants seem to up the KH. Apparently on APC a guy noticed some of hid Ludwigia were increasing the KH of the water, not sure of the mechanism for this or indeed if it was replicated. I was going to try it but the only ludwigia I have is L.helminthorhiza and it's not doing too well, maybe a spell in the greenhouse would do some bits good though...

    I'm sure you thought of these but that's all I can think of!
     
  3. Aeropars

    Aeropars Member

    Messages:
    779
    Location:
    Leicester
    Thanks for the reply.

    Its been a strange one really as i completly stripped this tank down a few weeks back so its all fresh tap water on an enclosed juwel tank so evaporation is minimal but it does occur.

    Test kit could be a possability although i think the massive difference between tap and tank is still right although the test kit could be out somewhat. I guess the only way to tell would be to get a new one.

    I know seachem onyx sand ups it slightly but it shouldnt do it by that amount. I think they say 0.1 to 0.2 kh. The tropica stuff shouldnt as its just a clay which they dont say anything about kh change. I dont beleive anyone else reported this either.

    Plants are just crypts, glosso, valis nana, hygro and anubias.

    My brain hurts!
     
  4. Ed Seeley

    Ed Seeley Member

    Messages:
    3,262
    Location:
    Nottingham
    Is it new sand? New calcerous material will leach more hardness as it hasn't got the coating of bacteria and things than old sand will have and none of the calrcerous material will have dissolved, but I agree with you, it's a big change from the tap water.

    I had problems with a replica root cave when I started keeping dwarf cichlids. It turned out it was made of calcerous material and kept upping the pH. ITts fine now and looks quite good with an Anubias gracilis on it!
     
  5. Aeropars

    Aeropars Member

    Messages:
    779
    Location:
    Leicester
    I did put 1 new bag in but the rest was old. I wouldnt have expected it to up the kh by that amount going on seachems claims.

    The dragon stone is a new addition but had the same high tank kh before. Its perfectly fine according to Richard at AE where I got it from.
     
  6. Ed Seeley

    Ed Seeley Member

    Messages:
    3,262
    Location:
    Nottingham
    Might be worth testing a bit in a glass jar just to see how much the KH climbs in 1, 2 or say 5 days. You may then be able to work out how much more water you'd need to change if you wanted to lower the KH. It would also prove it's the sand, or not!
     
  7. Aeropars

    Aeropars Member

    Messages:
    779
    Location:
    Leicester
    Incidentally, I just found out this from my water company website (Seven Trent)

    Hardness 103 mgCa/l (works out again to 5.7 kh)

    Going on that it looks like the test kit is measuring correctly as thats identicle to what I measured yesterday.

    It says on the classification on there that its hard water. Thats what washing machine companies woulc classify as hard but i thought it was pretty soft!
     
  8. Ed Seeley

    Ed Seeley Member

    Messages:
    3,262
    Location:
    Nottingham
    I'm not a 100% sure, but I thought that Ca was part of the General Hardness, not Carbonate hardness which is the buffering capacity, after all adding NaCO3 will up the KH but it doesn't have any calcium in it.

    And GH also includes Mg as well (if I remember rightly).
     
  9. Aeropars

    Aeropars Member

    Messages:
    779
    Location:
    Leicester
    Yes your right, i'm confusing myself again.

    Incidentally, i can get my PH down to 6.45 quite comfortably with the drop checker (4kh solution) only just showing green. If you look at a kh/ph relationship table (I know they are not accurate in the slightest) i would have a co2 level of over 100ppm. I only ever use this as an aproximate guide but even so, the normal relationships dont add up. My normal water is a ph of 7.5 ish.

    Nothing adds up in this tank and i'ts really frustrating.
     
  10. Ed Seeley

    Ed Seeley Member

    Messages:
    3,262
    Location:
    Nottingham
    That could be because something is lowering your pH. It could be tannins from the Redmoor wood, or maybe the Tropica substrate lowers pH like Amazonia Aquasoil. If anything apart from the KH or CO2 is present it makes those tables pretty useless for calculating the level of CO2.
    I looked into this as I have water of 0dKH and use Peat in my filter, before I would add CO2 as I was worried about the pH fluctuating wildly. I needn't have worried as, if anything, it seems more stable now (though i rarely measure it any more). But the cardinal tetras spawn every so often and other fish breed in there too.
     
  11. Aeropars

    Aeropars Member

    Messages:
    779
    Location:
    Leicester
    Well, i think i'll do 2 experiements.

    1. Sample the substrate and put it in a jar for a week. Test the fluctuation in KH

    2. Do a large wa\terchange and test immediatly after. Monitor throughout the week and see how much it fluctuates.

    I do fint it odd that noone has had this problem before. I'm almost wondering if I had a didgy bag of Onyx sand which is slowly disintigrating with the acidity of the water.
     

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