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Chemical Neutralisation of KH ?

Discussion in 'CO2 Enrichment' started by Rovik, Nov 4, 2012.

  1. Rovik

    Rovik Junior Poster

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    Hello all,

    Ill introduce myself as it is my first time posting here:

    I'm 17 years old from Australia and have been keeping fish since I was 13, My first tank was a simple planted nano and although have Kept a variety of fish along the way... but High Tech planted tanks are my where my interests Lay. Its great to see a dedicated, active forum for like minded aquatic plant enthusiasts.



    So here is my predicament,

    I have a 5'x2'x32'' aquarium which holds roughly 700L after gravel.
    The tank has been set-up now for over 2 months and during the set-up phase I used a product I was given, named "PenacP".
    Which for those who do not know is majority CaCO3 (98.1%) and the rest MgCo3.

    With this product, I sprinkled over the glass base of the tank and put my 80kgs of Inert Gravel over the top.
    I used this product to help neutralise the organic acids from an odd 18L of Aquasoil (Undergravel) that would have an effect on my pH, decreasing it and voiding the Rough C02/KH/ppm relationship void.


    I noticed the plants were quite sluggish in terms of growth the first 2 weeks and after a water testing I discovered that my KH' Was 14 degrees..
    My CO2 ran out very quickly as well (pH controller, Controlled) due to the High KH/base pH


    _____________________

    Obviously I have over done it with the CaC03 under the substrate and this is the reason why I have such a high KH. Silly of me.:(
    I have pH neutral gravel and My tap water is 3' KH.

    I after 6, 50% water changes a couple of days trying to dilute the KH:
    My KH went down to around 6 Degrees and the plants started to pearl madly for the first time since start-up.
    But sadly this was short lived: The water circulated slowly through the gravel and the KH is now sitting around at 12 degrees.

    _______________

    So... my question to the experts out there:

    Obviously I don't want to continue water changes for such a large tank to reduce my KH.
    So am I able to neutralise the KH chemically with a Acid Salt ? (I would prefer to dose with a dry salt rather than a aqueous soln of a strong acid- What do you recommend

    I have available Dry Pool acid (NaHSO4) but preferably I would like to use KHS04, as I have been told that the sodium Component will be undesirable In large quantities ???
    If KHSO4 or other, where is the best place to source it ?
    And if using the NaHSO4 (If suitable) How much ? My stoichiometry calculations yielded: 120g (NaHSO4) into a 700L of water, assuming 12 'd of KH.



    Thank you In advance.
    Rovik.
     
  2. Darkblade48

    Darkblade48 Guru Class Expert

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    Is it too late/too difficult to remove the material you placed underneath the Aquasoil? I cannot really think of any other method of reducing kH other than by doing water changes (either with your tap water or with RO/DI water).

    Of course, in a 700L+ aquarium, this becomes...tedious.

    Adding chemicals to the water is not the best idea either, since you will be increasing your TDS and playing with the water chemistry too much (shifts in pH/kH, etc)

    Perhaps some other people have some ideas...
     
  3. Rovik

    Rovik Junior Poster

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    Thanks Anthony.

    I think Removal of a non discript white powder under 80 kgs of gravel and aqua soil will be near impossible, and rescaping the tank is the last thing I want to do given how tall it is.

    Im certain that their is no cost effective way to dilute KH via RO water changed, most units are quite expensive and the entry level RO units just don't have the output for such a large tank, wasting more water than they put out.

    From memory, caco3 is only partly soluble in water (depending on pH) so if I am able to neutralise it with an acid then I can water change it out from there, still keeping my TDS low after water changing with readily available tap water (3KH). If can get it out of the gravel and into solution then it's easy pickings.

    Flush and refill from there.

    I could just flood the tank with more CO2 reducing the pH and therefor increasing the solubility of the CaCO3. But then I risk affixiating my fish.

    I want to add H+ without adding undesirable elements, but has anyone done this chemically ?
    If so what is the best to use?

    –––

    Antony: How important is TDS in a planted aquarium, I assume you would want to Maintain a hypotonic/isotonic solution depending on the plants ? My TDS can't really get any worse seeing as my KH is so high already. What to do, what to do.


    Thanks.
     
  4. Tom Barr

    Tom Barr Founder
    Staff Member Administrator

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    You can add HCL (pool stores sell it), but this can toast plants and kill fish if you are not careful.

    Most add it to the water they add back to the tank after the HCL has mixed and removed/destroyed the KH, then..........they pump the replacement water back into the aquarium.
    You can test and see how much it takes to remove the tap water's KH.

    The CaCO3 will stop adding HCO3- soon enough.........but water changes etc.......or removing it............are really the only 2 real options. The water changes are suppose to be done on new aquariums(like 50-80% 2-3x a week for the 1-2 months anyway..........). The KH should stabilize better with time.
    I'd just do the water changes, and maybe add a little HCL and then see how much it takes to drop 1 KH unit(17.86ppm). You can kill your fish if you are not careful FYI.

    So larger and more frequent water changes are likely the best option.

    Vinegar also works to destroy KH(5% distilled etc).
     
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