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Increasing pH - impact of Flourite?

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  • Increasing pH - impact of Flourite?

    I'm having a problem controlling the pH in my 40 gal planted + community tank.

    It's a new tank ... I've got 14kg of Onyx Sand (creates about a 1" layer) covered by an additional 14 kg of Flourite Red (another 1" layer). The tank is moderately planted (bamboo, swords, anarachis, anubias, etc.) with just a few Tetras, a Betta, and Pleco. There is a single piece of driftwood in the tank (purchased from LFS, and I boiled it for half a day before adding it to my tank).

    I dose the tank with Stability every day while the tank cycles.

    For filtration, I've got 200 micron filter socks for mechanical filtration followed by Matrix Carbon and Matrix for chemical and biological filtration. I've also got 350ml of De-Nitrate in a low-flow reactor.

    I'm using RO/DI water which I buy in 5 gal jugs. In each jug I add:[LIST][*]3.5g of Alkaline Buffer[*]1.8g of Acid Buffer[*]8g of Equilibrium[*]Fresh Trace - 1.25 mL[*]Flourish Trace - 1.25 mL[*]Flourish - 0.5 mL[*]Stability - 2.5 mL[/LIST]Before adding to my tank, each jug tests out at:[LIST][/LIST][LIST][*]pH 7.0[*]KH 100 mg/L[*]GH 180 mg/L[/LIST]When I initially setup the tank, the initial readings were pretty close to this. However, within 24 hours the pH was over 8.2 and the KH had dropped to 60 mg/L.

    I would slowly add Acid Buffer (in approx 5 g increments every few hours) to bring the pH back down, and then dose both Alkaline Buffer and Acid Buffer together in a 2:1 ratio to restore KH. However, each time the pH would again climb to over 8. I've been doing this every day for about a week with the same outcome each time.

    So I did a 50% water change (same water, same initial doses) and the pH came back down to 7.0.

    However, once again, within 24 hours the pH is back to 8.1 . Here's a screenshot from my Apex controller of the pH (yellow) and Temperature (black) plot over the past 24 hours. You can see where I performed the water change at the left, and then added more Acid Buffer on the right. [ATTACH=CONFIG]n21901[/ATTACH]

    What am I doing wrong?[LIST][/LIST]

    Attached Files

  • #2
    [FONT=georgia, serif]Thanks for the post evangemeren! What method are you using to measure the kH? this kind of sudden drop is usually associated with a strong acid source, but it doesn't sound like you have anything like that in your tank. Have you tried measuring the treated water and waiting about 24 hours to then measure it again to see if without the Onyx sand, the pH will shoot up? [/FONT][FONT=georgia][SIZE=16px]Onyx Sand is not chemically coated or treated but does have a slight buffering capacity that may raise pH by 0.1 - 0.5 pH units (depending on source water characteristics).[/SIZE][/FONT]