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Thread: pH question

  1. #1

    Join Date
    Jun 2014
    North Georgia

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    Default pH question

    0 Not allowed!
    Hello ,
    I have a perplexing problem . My tap water , after gassing out for 24 hours , is at pH of 7 ish , my tanks are all cycled and I do weekly water changes , have top of the line filters , do not over feed , and tanks are not overcrowded , but , the pH drops after a few weeks and stays there . I know that I can just let the fish get used to the pH level , but I am just curious as to why it drops when I think I am doing everything correctly . All tanks have regular gravel , plastic plants and ornaments , and one has some live plants . I have tried using crushed coral in the filters and no change . I have had tanks for years and never worried about it ,maybe I am just over thinking lol

  2. #2

    Join Date
    Aug 2012
    Elgin, Illinois USA

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    0 Not allowed!
    What do you mean by 7 ish? Is it 6.9, 7.0, 7.2? What does the pH drop to after 1 week, just prior to your water change? I don't see how it can drop after a few weeks if you do weekly water changes. You would be adding water that is "7 ish" and that would raise the pH till the next weekly water change where the same thing would happen all over again.

    Also, what is the dKH (degree of carbonate hardness) of your water? You can get this info from your city water dept. If you dKH is too low, your water is not buffered well and the pH will not be stable and will drop. You need a dKH of 2-5 to stabilize your pH.

    If it's not a big swing, you may not need to worry.
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  3. #3

    Join Date
    Jun 2014
    Auckland, New Zealand

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    0 Not allowed!
    + 1 to testing your carbonate hardness. Low carbonate hardness can make your water more susceptible to pH swings.

    pH can drop over time (eg over the week) for a variety of reasons. Those with CO2 can have the pH change throughout the day. For a lot of fish accurate pH is less important than consistent pH.
    If you have
    - Peat moss
    - Driftwood
    - Leaf litter
    - Rotting plants
    Your pH will probably drop a bit over the week (especially if you have a low dKH)

    If you have
    - Coral rock
    - Limestone
    - Crushed oyster shell material
    - Shells
    Your pH will probably rise over the week.

    pH changes as tanks get older and older tanks can develop "old tank syndrome" where the pH drops and can easily swing.

    A low drop during the week I wouldn't worry about but if it's caused by one of the above and eg drops from 7.8 to 7.0 I'd be either buffering your water to 7.0+ (eg running it through a filter with peat moss) before putting it in the tank or doing multiple smaller water changes to avoid major swings.
    Edit to say definitely be wary if doing water changes and your pH is a lot lower than your water. I stupidly hadn't tested pH in a while and did a 50% change, and accidentally shocked one of my black neon tetras. The tank was old and running with a lot of driftwood, and the pH was sitting at about 6.4 - my water sat at 7.8. Typically I only do 25%s, but was doing a larger change that day which evidently was enough to cause some major issues.
    Last edited by Tetraodon; 06-14-2014 at 02:04 AM.
    120L Planted community, 220L Planted community, 55L Killifish & hara cat, 31L Dwarf puffer tank

  4. #4

    Join Date
    Jun 2014
    North Georgia

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    1 Not allowed!
    Thanks for the replies . I will check and work on the hardness angle .

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