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Thread: High CO2 ppm even with 1 bubble/sec

  1. #1
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    High CO2 ppm even with 1 bubble/sec

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    Tank Dimensions (LxWxH, specify units):3"x1.5"x1.5"

    Lighting Intensity(No of Watts) : 144
    Number and type of Lighting (FL/PL/MH) : PL
    Age of light bulbs : 30 days
    No. of hours your lights are on : 10

    CO2 Injection Rate (bps) : 1
    Type of CO2 (DIY/Cylinder) : Cylinder
    Method of Injection (e.g. Diffusor/Reactor) : Internal Reactor

    Liquid fertilisers Used (Product name. E.g. Seachem Flourish) : Lushgro Micro, Lushgro K2SO4
    Fertilization regime (Frequency and amount per dose) : LGM: 4 drops/week, K2SO4: 3ppm/week

    Other fertilisers (Product name. E.g. Root Monster) :

    Other additives (Product name. E.g. Seachem Prime) :

    Type of Filter (overhead/internal/canister, Product name/model if possible) :
    When was the filter last washed : 3 weeks ago
    Filter media used : Fine+Coarse filter wool, bio rings, sintered glass
    When was the media last changed :
    What was changed :

    Age of setup (i.e. since initial setup or last major re-do ) : 2year +

    Water change frequency : Once per week
    Amount changed : 30-50%

    Water surface movement (None/gentle/turbulent) : Gentle
    Circulation (None/gentle/turbulent) : Gentle

    Tank Temperature : 29 deg cel

    Chemical Properties (Fill what you can)
    -------------------------------------
    KH (dKH): 4
    GH (dGH):
    pH : 6.5
    NH4 (ppm): 0
    NO2 (ppm): 0
    NO3 (ppm):
    PO4 (ppm):
    Fe (ppm):

    Bioload (Number and type of fish and plants)
    ------------------------------------------
    8 cories, 2 SAE, 7 yamato shrimp, 4 tetras, 1 puffer fish.

    Describe your problem :
    ----------------------
    My CO2 concentration (according to "Chuck's Planted Aquarium Calculator v1.0i") is 38ppm even though my CO2 flow rate is just 1 bubble/sec, and my tank is moderately planted. Is this considered a dangerous concentration level? Half an hour before the lights are turned on, the CO2 concentration can get as high as 90ppm. Thankfully, all the animals are fine. I have searched through the forum, and found that some forummers have CO2 rates of 2bubbles/sec for a 2" tank, and 3+ bubbles/sec for a 3" tank.

    So... should I crank up the CO2 further?

    Other than peat, and additives like Seachem Discus Buffer, what other chemicals could invalidate the KH-PH-CO2 relationship?

    Thanks a million.

  2. #2
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    Looks ok to me... keep it as it is so long as the animals are ok and algae is under control. Anyway, bubbles-per-second is a meaningless measure, as you probably know already.

  3. #3
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    Sounds like you are doing CO2 24/7 which you really don't need to. Plants only use CO2 when the lights are "on". Try shutting off the CO2 at night to see how things go. Target 30ppm when the lights are "on" is what you only need to do. Error on the high side near 30ppm and watch the animals. By the way, what kind of equipment are you using to test for the pH?

    Regards
    Peter Gwee

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    Thanks, Budak.

    Peter: Yes CO2 is "ON" 24/7. I read somewhere that the use of a solenoid may cause a large variation in the CO2 level, especially if the CO2 level is set too high, furthermore the water will not get to a high-enough CO2 level just before the lights-on period, so the plants will take a longer time to photosynthesis at the peak efficiency. Is there any truth to those two arguments against the use of a solenoid?

    Anyway those are just theories. In practice, does the solenoid work well in your setup? Do you have a "siesta" period during the lights-on period? I have a 4 hour rest time during the 10-hour photo period. The plants take about 2 hours to start bubbling, both times the lights are turned on in a day.

    I use a Tetra kit for testing pH, and a JBL for testing KH. I also use a Sera kit to check for CO2.

    Thanks again.

  5. #5
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    From the CO2 chart, it looks like if the pH is 6 or lower, the CO2 ppm is always high, worse when KH is higher. So if some factor likes ADA soil that brings down the pH, does it mean the ppm is always on the high side, even though the CO2 supply is low?

  6. #6
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    Quote Originally Posted by MosFat
    Peter: Yes CO2 is "ON" 24/7. I read somewhere that the use of a solenoid may cause a large variation in the CO2 level, especially if the CO2 level is set too high, furthermore the water will not get to a high-enough CO2 level just before the lights-on period, so the plants will take a longer time to photosynthesis at the peak efficiency. Is there any truth to those two arguments against the use of a solenoid?
    Yes, the CO2 will go down (pH goes up due to degassing) if you shut it during the night but there is no good reason to inject CO2 at night (plants don't use it). We inject CO2 for plants as a nutrient, not for pH control. If you have issue getting the CO2 to the good range (20-30ppm) within an hour or so after it is turned on, consider better mixing methods.

    Quote Originally Posted by MosFat
    Anyway those are just theories. In practice, does the solenoid work well in your setup? Do you have a "siesta" period during the lights-on period? I have a 4 hour rest time during the 10-hour photo period. The plants take about 2 hours to start bubbling, both times the lights are turned on in a day.
    Unless you have an issue with keeping good CO2 levels during the photoperiod, there is no good reason to have siesta. Go for a straight 10-12hr photoperiod.

    Quote Originally Posted by MosFat
    I use a Tetra kit for testing pH, and a JBL for testing KH. I also use a Sera kit to check for CO2.
    Consider a more narrow range pH test kit (0.2 intervals like the AP I think) or better, a pH test pen/monitor.

    Regards
    Peter Gwee

  7. #7
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    Quote Originally Posted by lwm999
    From the CO2 chart, it looks like if the pH is 6 or lower, the CO2 ppm is always high, worse when KH is higher. So if some factor likes ADA soil that brings down the pH, does it mean the ppm is always on the high side, even though the CO2 supply is low?
    Well, that is why I don't recommend new folks to use ADA soil unless they know how to get about that measurement issue. You can go about it in 2 methods though but then again there is some play as well with pH/KH methods.

    Regards
    Peter Gwee

  8. #8
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    I have installed the solenoid, and removed the siesta period. The photo period is now a contiguous 10-hour block.

    But now the plants take almost 3 hours after lights-on to start bubbling (as opposed to 2 hrs previously when CO2 was "ON" 24/7). I suspect that the internal reactor is not dissolving CO2 as efficiently as it should. Fine bubbles are shot out of the reactor constantly. Is this supposed to happen?
    Attached Images Attached Images

  9. #9
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    You used to have CO2 24/7, that means your water is usually almost full of gases. That's why your plants bubble faster. Now you only inject CO2 during the lights on period, it takes time for the gases in the water to build up so that oxygen produced by the leaves will show as bubbles instead of dissolving directly into the water.

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    Quote Originally Posted by |squee|
    You used to have CO2 24/7, that means your water is usually almost full of gases. That's why your plants bubble faster. Now you only inject CO2 during the lights on period, it takes time for the gases in the water to build up so that oxygen produced by the leaves will show as bubbles instead of dissolving directly into the water.
    Use a separated timer for your solenoid and turn it on 1-2 hours earlier? And turn it off 1 hr earlier too maybe?
    Cheers and Regards,
    Billy Cheong

    I'm not always dumb,
    Just most of the time...

  11. #11
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    Thanks Goondoo, Squee

    I think the lack of plant activity could be due to the lack of nutrient. I did a test on the water in the morning, before the lights and CO2 came on, and the CO2 concentration was 38ppm. Don't know how it got that high. The day before, when my CO2 was at 2 bubbles/sec, the CO2 cont. was 90ppm!! I had already added LGM, KH2PO4, K2SO4, and with the CO2 at 90ppm, there was zero activity. So yesterday, I tried adding some Lushgro Aqua, and following that I started seeing bubbles again. Well at least there is some improvement.

    PeterGwee: I bought a JBL test kit from Keong Seong as their shop is closer to me. The kit is also able to give readings to a precision of 0.2, but then it is more costly than the Aquarium Pharmaceuticals one.

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