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Thread: Low pH in the tank

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    Default Low pH in the tank

    Hi Everyone

    I'm just getting set up to keep discus for the first time and I'm trying to make sure I'm prepared.

    One of the things I've picked up on this forum is the importance of water changes and the stability of water chemistry, temperature and

    My aquarium, has a mature canister filter from a previous tank, it's bare bottom, has an air stone and only 6 zebra danios. I siphon hose out every two days and replace 20% water, the water is crystal clear.

    I'm from a Scotland so our tap water is very soft, it comes out the tap at ph 8-9. After aging in my water barrel with heater, air stone and pump for agitation it settles at ph 7.2.

    The issue is that the tank is sitting at a constant pH 4.6, I don't want to be adding water of 7.2 when I've got discus in that tank.

    Can anyone help?

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    Registered Member dandestroy's Avatar
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    Default Re: Low pH in the tank

    Can you measure the hardness of your water (TDS meter, or GH/KH kit)

    Adding 20% water at 7.2 to a 4.6 is not that bad, the fish should be ok. But I am concerned about your 4.6 to start with

    if your water is soft it will have a low pH.
    so if it's coming out of the tap at 8-9 (assuming it is indeed soft, which it may not be until you measure it), probably that your city is adding NaOH, you could ask your city to confirm.

    I'm not a fan of canister filters, as they are just a giant trap for gunk. Maybe try doing a really good cleanup of it, or do a test running your tank on a air-sponge filter only (the goal would be to see if your canister is causing the low pH or not). You could add crushed coral to your filter or tank to help buffer the water quite a bit and that would keep the pH higher.

    All that said 4.6 is very low. Discus can deal with wide pH ranges, but I would like to figure out why it goes so low.

    To put it in perspective, here in Seattle area, the water comes out extremely pure (TDS <30 ppm). They do add NaoH to the water, so it comes out around 8.5. Once in the tank, it settles at 6.8 after a few hours and stays there forever (bare bottom, running a sump with porret foam, and filter rocks, clay, etc). I have ran these tank on air-sponge only with identical result.

    I don't age my water, and I do a 90% weekly, here is a graph of my pH fluctuation. the peaks are when I do water changes


    FrancK
    2018 year of the big tank!!!.

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    Registered Member Shaun's Discus's Avatar
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    Default Re: Low pH in the tank

    Sounds like you have no KH which is making it drop so low. I use small stockings with crushed coral to help protect from PH crash and keep the tank buffering at the same PH as the water you add when doing W/C's

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    Default Re: Low pH in the tank

    Hi Folks

    Thanks for your input.

    My cannister filter was already pretty clean, i clean it weekly, however the pipes were old and had never been cleaned, I've replaced those and I've seen a marginal increase in pH - so thanks for that suggestion.

    So I'll try the crushed coral next!

    Thanks
    C

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    Moderator Team LizStreithorst's Avatar
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    Default Re: Low pH in the tank

    Please check your kH for us.
    Mama Bear

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    Default Re: Low pH in the tank

    I'll need to get a kit to test kH.

    In the meantime I've added crushed coral, put it into the cannister filter, pH has settled all the way back up at 8.5 and is stable.

    Is this too high now?

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    Moderator Team LizStreithorst's Avatar
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    Default Re: Low pH in the tank

    It's fine as long as it's stable. We still need to know your kH. It's either the kH or Gh that is making your pH so high.
    Mama Bear

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    Registered Member bluelagoon's Avatar
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    Default Re: Low pH in the tank

    Some areas have very little KH in their water ways. This is mostly due to where and how the water makes it to the reservoir. Usually coming from the surface and running through a humus soil, moss, old wood, ect. So, the water suppliers will had things such as sodium hydroxide to bring PH up to hinder pipe erosion. After aging you may or may not see a ph swing, but in you tank the ph will sometimes go down in a very short time due to ion exchange(- +) from metabolized waste which depletes the bicarbonates that holds the ph stable. Now that you have tried the coral and your ph is over 8, all you need now is to find out the amount of coral that keeps your tank stable, less coral is likely in this case.

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    Registered Member cooper666's Avatar
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    Default Re: Low pH in the tank

    At pH 4.6 your biofilter will be starving for carbonates and will pretty well stop working.

    You can add sodium bi carbonate to lift the KH and pH. General rule of thumb is to add about 0.3g of bicarb for every gram of feed (very rough guide)

    Generally, an increase in pH during aeration / ageing of water is caused by stripping dissolved CO2 from the tap water, thus pH goes up.

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    Moderator Team LizStreithorst's Avatar
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    Default Re: Low pH in the tank

    sodium bi carb will raise the carbonates for a short time, then then the kH and pH will crash. The constant swing will be bad for the fish over time.
    Mama Bear

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    Default Re: Low pH in the tank

    I also have issues with low carbonate hardness in my tank (it is barely even 1, where it used to be 4, (explains every issue I've had). I would be curious to know how much crushed coral you used to settle the problem, my tank goes to 5 within hours where from the tap it's 7.6. Aging barrel also stays at 7.6. I do twice daily water changes right now to battle this issue. I'm afraid the crushed coral will bring it too high but I'll take it at this point.

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    Registered Member bluelagoon's Avatar
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    Default Re: Low pH in the tank

    Try small amounts, like a small handful at first, in a nylon sock, in your filter. Then adjust accordingly. Aragonite will work if your can't find coral.

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    Silver Member Tanja's Avatar
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    Default Re: Low pH in the tank

    Quote Originally Posted by bluelagoon View Post
    Try small amounts, like a small handful at first, in a nylon sock, in your filter. Then adjust accordingly. Aragonite will work if your can't find coral.
    Will do! Thank you!

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