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Thread: CO2/pH/KH table

  1. #11
    Well, CO2 doe sNOT change that much at lower ppm's, it changes a lot at the higher ranges. When folks belly ache about not being able to add CO2 because it gases their fish at above 20-30ppm, it's because they are winging it and not being careful, going slow and watching.
    Perhaps their O2 is poor, perhaps there's surface scum, perhaps the CO2 equipment is hard to adjust precisely and accurately.

    Damn, there's 101 ways to screw CO2 up.
    This is more an issue for folks trying to tweak things, GO SLOWLY.

    As you increase the CO2, you also decrease the changes you make and a SMALL change in pH = a huge change in CO2.

    I see this in my 120, the 180 has a higher buffer of CO2.
    A change of 0.2 pH units will result in glass algae and hair algae in the 120.
    But that's about 20 ppm worth of CO2!!!!

    Which is a lot frankly.

    I keep trying different ways to explain this, I have done it 101 ways so far, and I'll think of more at some point also.
    People really have a simple understanding of CO2, which is unfortunate.

    Hopefully over time, I can change that view.

  2. #12
    Join Date
    Sep 2009
    Kettering, Ohio, United States
    I measured some tanks in Ohio USA that had according to the chart, 220 ppm of CO2.
    No driftwood or anything like that. Fish were fine.

    Curious where in Ohio?

  3. #13
    Near Cincinnati, it's all limestone karst aquaifer.

  4. #14
    Join Date
    Sep 2009
    Kettering, Ohio, United States
    That was my guess. I'm right outside Dayton. Cincy is ~30-45 mins away.

  5. #15
    Join Date
    Sep 2009
    Kettering, Ohio, United States
    Just tested my tank and it fell dead on the chart....4.5 kH, 6.2pH and 66 ppm (no livestock in tank). This means I can turn back the CO2 and just watch the pH to dial it in most likely. It will be interesting to see how much CO2 I can get in without gassing the fish/shrimp..going to start at 30 ppm, which should be around 6.55 pH.
    Last edited by UDGags; 03-03-2013 at 05:17 AM.

  6. #16
    You have to be careful anywhere there's karst limestone in the water table. Sounds like that might be surface river water, not well water.
    3.5KH is likely surface, not well. Might be a little non carbonate hardness in there. Still, not likely more than 1-2 degrees.

    If you have a wet/dry, 66 ppm seems fine.

    If not, etc, maybe 40-45 ppm might be the limit.

    Cranking the surface current will help maintain a higher CO2 threshold also if you do not have a wet/dry.

  7. #17
    Join Date
    Sep 2009
    Kettering, Ohio, United States
    I actually just retested and came up with 4.5 dkH. I tend to believe the 4.5 since its what my tap water is at....doesn't really water matter just gives me a reference point.

    I'm part of the Miami Valley Buried Aquifer. I'm a bit too far north. I have a few friends that are in the limestone one. I know my ex-gf was in it.

    Yes, I have a wet/dry sump and I have a vortech at the surface making waves. I think the 66 ppm will be fine but will start lower and work my way up slowly.

    Off-topic but have you measured your 180 dissolved oxygen? I know you said you ran it at 60-70 ppm CO2 and the fish were fine. I have a LaMotte test kit for dissolved oxygen and wanted to compare.

  8. #18
    It ran consistently at 100% with the lights off all the time.
    During the lighting period, it rose to about 125-130%.

    This was at about 84F, so the ppm is about 7.7 ppm to about almost 10 ppm, a jump of about 2 ppm

    The canister set up never got to 100% except during the light cycle and then only about 1 hour or so.
    So the claim was 1-2 ppm increase in O2 for all my tanks that were canister that got converted to Wet/drys.

  9. #19
    Along those same lines as CO2 changing as you go to the higher concentrations, the temperature also plays a huge difference with metabolism of fish, and the ambient O2.

    84F( or about 28.9 C) the O2 = 7.6 ppm.
    At say 70F(about 21 C) the O2 is nearly 9 ppm.

    So you have 20% higher O2 ppm and you do not need a heater.
    Plenty of O2, slower rates of growth, less energy cost.

    This can make a huge difference in the aquarium.

    Say you just want some Amano shrimp, CRS, RCS etc, and say White clouds, then this is a great way to have a planted tank.
    68-72F seems to do very well for most species.

    Algae and dosing are much easier to manage.

  10. #20
    Join Date
    Sep 2009
    Kettering, Ohio, United States
    Thanks, that makes sense.

    Otos/amano's are my cleaning crew. Looking into getting a couple unique plecos and than probably a shoal of tetras (or something that won't bother the shrimp). Once I figure out the fish exactly I can fine tune the temperature.

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