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Beginner question: Stabilize Ph at 6.8 using Acid and Alkaline buffer

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  • Beginner question: Stabilize Ph at 6.8 using Acid and Alkaline buffer


    I’m a beginner, sorry me if these are dumb questions, my tank has only a couple of days.
    I have a freshwater tank and I want to keep Ph stabilized in 6.8. I was recommended to use both Acid Buffer and Alkaline Buffer to do this, but I don’t know how to use them. I’ve made some researches in the forum but I’m still in doubt.

    I’m not familiar with terms like Kh, Gh and so on, what I know is:
    - My tank has 100 liters of water.
    - I’ve used tap water to fill it. I live in Sao Paulo, Brazil, water quality is good (we can even drink it) but it’s too alkaline for my needs, it came with a Ph of 7.5.
    - My fishes need soft water.
    - My substrate is PH neutral.
    - I have no shells or other stuff that raises my Ph.

    My questions:
    - Since tap water comes with Ph 7.5, what doses of Acid Buffer and Alkaline Buffer I must use to make Ph stabile at 6.8?
    - Must I put them together in the water or Acid Buffer first then Alkaline?
    - What are the recommendations to keep Ph stabilized during water change?

    Someone could help, please?

    Thank you in advance!

  • #2
    Thanks for the post! Before I answer your direct questions I will explain the difference between the terms you mentioned. :)

    KH is part of your alkalinity and is a measure of your carbonates and bicarbonates in the water. Alkalinity and KH help to stabilize the pH, so you always want to maintain a good level.

    GH is your general hardness and is a measure of the calcium and magnesium ions in the water. Fish and other inhabitants need these minerals in the water so that they can osmo-regulate properly (the maintenance of constant osmotic pressure in the fluids of an organism by the control of water and salt concentrations), so maintaining this element in the aquarium is also very important. For example, if you were using RO water, which is completely stripped of all elements and considered extremely soft and pure, you would add a GH supplement to increase that level. For most freshwater tropical aquariums, the proper GH is anywhere from 4-8 dGH.

    Now I will answer your questions in the order they were asked for sake of clarity:

    1. Since your tap water is high in bicarbonates (pH of 7.8), you will first want to use the Acid Buffer along to bring down the pH closer to your desired level. For 100 liters, I would add a single dose of a little more than 1/4 teaspoon (5/16 to be exact) to the water until you are able to bring the pH down to around 6.8-7.0. Once you have reached a more desirable pH, you will add the buffers together to lock it in place. You will add the following amounts to 100 liters:

    1 1/4 teaspoons of Alkaline Buffer
    3/4 teaspoon of Acid Buffer

    Keep in mind that these ratios are meant for RO water, so since you are using tap water you may have to play around with the ratios until you get your desired results. If you find that the pH is not low enough, increase the Acid Buffer, if you find that the pH is too low, increase the Alkaline Buffer.

    Once you have found your ratio for your tap water, write it down so you will know exactly how much you will need to add in the future, mainly at water changes to adjust the pH.

    I hope this helps! Let us know if you need further assistance!


    • #3
      Thank you, so much!


      • #4
        You are very welcome!


        • #5
          Hi I'm very new in here, but I'm struggling with the same subject -> Equilibrium/Alkaline/Acid buffer ratios 🤔
          I did measure 5 UK gallon [22.73L] in my bucket and this is the volume I'd like to use for routine water change.
          Some very kind aquarist did his best to help me out with math, and he did provide me exact buffer ratios related to my 5 UK gallons of RO water.
          Equilibrium = 4.8 grams
          Alkaline = 1.6 grams
          Acid = 0.72 grams

          My RO water has hardness of 8.6PH.
          The above ratios is supposed to give me around 200 TDS, and around 6.8 PH.
          I was also adviced, that I don't need to lower the PH of my RO water before adding mixed buffers to the bucket.
          I am not questioning this advice.
          All I'm after is to ask you (admin please) if you can agree/confirm, or correct it if necessary please?

          I have 520L planted freshwater (I'm aiming to keep it darker - black water) aquarium.
          At present it's around 7.3PH, at room temperature (22°C), KH 3, GH 17 (it was 37, and went down recently thanks to RO).
          I've started replacing the tap water with 5 UK gallons of RO week by week -
          to make the whole switch as harmless as possible...
          So far so good, no fish loss other than 2 Cardinal tetras, but I have them for 2 years, it might be caused by the switch, or by their age or else, I'm not sure...
          Apart of these two fish, everything else is as normal.
          I'll be appreciated for kind reply, your thoughts, and/or advice please...
          Thank you in advance.
          Last edited by PogArt; 05-11-2022, 15:40.


          • #6
            Thanks for the post, PogArt!
            Can you please tell us your desired KH? As far as lowering the GH, this will need to be done through water changes with RO water, as we do not have a specific product to soften the water. I would just hold off on adding Equilibrium until your GH has dropped to the desired level in the aquarium.