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Time from CO2 turn on to reach correct level?

Discussion in 'CO2 Enrichment' started by ibnozn, Dec 4, 2008.

  1. ibnozn

    ibnozn Member

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    I have my CO2 on a timer set to turn on an hour before my lights and off an hour before the end of my photoperiod. From the CO2 switching on @ 8:30 am it is not until at least 2:30pm or so until I get a ph/kh reading indicating 30ppm. My CO2 indicator color also seems to confirm that this is about how long it takes to reach good CO2 levels in my tank. It's set around 1.6 - 1.7 BPS. Faster bubble rates tend to push the saturation really high by the end of the photoperiod. I've gone beyond 50ppm a few times before having to shut it down to avoid gassing fish. Still, it seems awfully long to reach correct levels doesn't it? It's a 20G and I'm using an inline Grigg style reactor. Would I be better off speeding up the bubble rate so it comes up faster but switching the gas off intermittently during the photoperiod to keep it in the right saturation range?
     
  2. Tom Barr

    Tom Barr Founder
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    30 minutes to 1 hour is decent.
    I measured a large 1600 gallon system and it jumped to 30ppm in about 40 minutes.
    Smaller tanks should be similar if not better.

    Regards,
    Tom Barr
     
  3. detlef

    detlef Member

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    Tom, from what you've measured in a large 1600g system can we deduce that there is a big difference in CO2 concentration judged by pH drop vs. " precise direct" measument? I suppose that due to large lag times for the pH to drop after CO2 injection tanks should have reached target CO2 levels much earlier than what we've previously assumed by the pH status. This would make CO2 injection kicking in more than one hr previous to lights on absolutely silly for small/middle sized tanks with responsive CO2 devices.

    Best regards,
    Detlef
     
  4. SuperColey1

    SuperColey1 Guru Class Expert

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    If you wanted to know the exact colour indication from your DC for lights on then you would have to know the delay time within the solution/DC.

    IMO this can vary from DC to DC and the amount of solution used etc.

    I ran a test a few weeks ago, one on the traditional style glass Chameleon DC and the other the old teardrop style. Both had 1ml in them but the Chameleon changed much much quicker to a lighter colour.

    Therefore I think it is impossible to say how long the 'lag' is within the DC as each is different.

    IMO It should be safe enough to assume that if the DC hits yellow at all during the day then you are hitting reasonable levels unless you have no CO2 usage within the tank (plants etc.)

    I judge my DC colour 2 hours after lights on as being the 'rough' lights on measurement.

    Oh and I also turn on 1 hour pre lights but turn off 3 hours pre lights off.

    A little timeline of the test (3pm is 1 hour before lights on and 9pm is when CO2 stops):
    [​IMG]
    AC
     
  5. rich815

    rich815 Guru Class Expert

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    I have my CO2 go on 2 hours before my lights do. My lights go on a 2pm and run until 10pm. When I look in the dark tank at 8am before work my drop checkers are green-blue. When the lights go on at 2pm they are green (deep), by 3-4pm they are light green even leaning towards yellow. By 9pm they are lime yellow-green. Consider having your CO2 go on 2 hours before lights.
     
  6. Gerryd

    Gerryd Plant Guru Team
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    Hi,

    I played around a lot with this and finally settled on the following for my 180:

    C02 ON 90 minutes PRIOR to lights on.
    C02 OFF 60 minutes PRIOR to lights off.

    Have had this schedule now for 3-4 months and is working for me.

    I agree with supercoley1 that EVERY tank and possibly DC is different.

    Later,
     
  7. detlef

    detlef Member

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    What I meant wasn't the DC for judging CO2 levels. They are at best a rough estimate after all (even though the best we know of thanks to hoppy).
    But absolutely useless for estimation whether CO2 is at 30ppm when lights come on. Due to imprecision and long lag times. Let alone differences between brands.

    We have 3 possibilities for getting an idea how much CO2 we have when lights come on :

    1. DC, useless see above
    2. pH measurement, quite useless because CO2 takes time to generate carbonic acid (nice work by the way SuperColey1)
    3. direct testing for CO2 (Tom's method, yes again!)


    And this is my point here: We know plants grow at max speed into the early hrs of the photoperiod. Right at the beginning with lights on we should aim for 30ppm. In the past I measured pH at 30min's intervals to know when CO2 hits the 30ppm mark. Now with Tom's testing (i.e. CO2 results immediately when measured) it's reasonable to assume that CO2 raises much faster than what we previously have deduced from pH measurements. Hence my asumption that CO2 never needs to be started more than 1 hr before the lights come on even for really big tanks as Tom found out.
    Remember even Amano lets CO2 kick in no earlier than with lights on. In the end he seems to know quite a bit!

    Best regards,
    Detlef
     
  8. Tom Barr

    Tom Barr Founder
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    Yes, but that assumes they are actually adding enough CO2 to begin with relative to plant demand.

    If not, then adding a lot at the initial STAGE MIGHT HELP. Basically feeding a slug into the system and then running lean on CO2 from then on.

    Otherwise, yes, you are likely correct.
    I add CO2 with the lights.
    Amano does typically also.

    Regards,
    Tom Barr
     
  9. Tom Barr

    Tom Barr Founder
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    I think both myself and Amano has one thing certainly in common, we watch the plants pretty carefully also.

    We both do large water changes and tweak CO2 mostly by eye.
    He uses less light than most seem to assume/think.
    We both also add CO2 only during the light cycle.
    I always have, so has he for the most part as well.

    You'll note I test after I see good conditions, not before. I want to know why, what those the conditions are that are causing good health, growth and no algae.
    I came up with EI after seeing if it would work, then went back and tested it.
    Not the other way around.
    Same for PO4, I had no clue I was adding it from the tap water(ADA also has relatively high PO4 in the tap for the light levels they use).
    Later, I tested, same deal with ADA's lighting systems

    I do not care much about algae, nor poor plant growth. That's where many who question are at though:mad: They are only concerned with test kits, solving the "issue", not seeing what a successful tank does.

    Folks want the total explaination why their tanks are not doing as well, but many times, they do not focus as much as they likely should on the plants.

    Riccia is a really good CO2 indicator plant IME.

    Regards,
    Tom Barr
     
  10. SuperColey1

    SuperColey1 Guru Class Expert

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    I tend not to use the drop checker to check if I am at a certain level for plants. I tend to just push the CO2 as high as it will go without turning the DC yellow at any stage in the day.

    I'm not overly concerned what the level reads or is at lights on as long as there is enough there for the plants and the fish aren't harmed. If this means it is at 15ppm at the start and slowly builds to 30-35 at its peak then this is fine.

    After all there doesn't 'need' to be 30ppm at lights on. There needs to be 'enough' throughout the photoperiod to satisfy the plants needs. If the level is rising through the photoperiod then the plants aren't using as much as is being injected thus making the level (IMO) satisfactory!!!

    AC
     
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