• How To Lower pH ?

    pH (potential of Hydrogen) is one important water parameter to monitor for keeping fish. Most people face difficulty in decreasing it then raising it. So, I’m trying to compile a simple one-stop information on various methods used to lower the pH (to the best of my knowledge) for the benefit of AFT members. Your contributions are very much welcome. I will continue to update this article whenever new information is collected.


    Peat is quite effective in lowering the pH. However, its humic acid and tannic acid turn the water into brown colour. Commonly used products are:
    1) Sera Super Peat
    2) Amtra
    3) Eheim Torf


    Driftwood can be used to lower pH, but the result is slow, probably need to wait till the wood starts to rot then it will release more tannic acid.


    Not so effective in lowering the pH.

    Ketapang Leave

    Not so effective in lowering the pH.

    pH down solution/powder

    Most pH down solution/powder contains phosphate which promotes the growth of algae. Phosphate is a fertilizer for plants. Commonly used products are:
    1) Seachem Discus Buffer
    - Phosphate based, not suitable for planted tank
    - Lower pH and soften water by precipitating Calcium and Magnesium ions
    2) Seachem Acid Buffer
    - Non-phosphate based (no algae problem)
    - Lower pH and converts carbonate alkalinity (KH) into CO2
    Above two products are quite effective and safe in lowering pH.

    Artificial vinegar (acetic acid and citric acid)

    Not so stable, after awhile the pH will shoot up.


    CO2 dissolves in water to form carbonic acid which in turn lowers the pH.

    Rain water

    Rain water is quite acidic. With a low KH, the CO2 dissolves in it can easily bring down the pH. Usually the pH is in the range of 4 ~ 5. Rain water is an economical option for lowering the pH of a big pond as it is free.

    Distilled water & reverse osmosis filtered water

    With a low KH, these waters can help to lower the pH. But, it is an expensive solution.

    Fish bioload

    Hydrogen ions and nitrates are the end products of nitrification cycle occurred in the bio-filtration system. Increase in hydrogen ions will cause the pH to drop. Usually for tank with one fish, poor appetite or low bioload, the pH will remain high.

    Concluding Remark

    To lower the pH, first make sure there is no substance which buffers KH, such as coral chip, oyster shell, clam shell or any sea shell. Also, those cheap bio-glass rings (made in China) may buffer the KH. Once the KH is depleted, the pH will drop.

    After trying a few methods, Seachem Acid Buffer is currently my choice of lowering pH.
    This article was originally published in forum thread: How To Lower pH ? started by neosh View original post

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