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CO2 'lead' time

Discussion in 'CO2 Enrichment' started by scottward, Jul 2, 2010.

  1. scottward

    scottward Guru Class Expert

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    I'm hoping to encourage some good discussion on this one... ;-)

    CO2 'lead time', 'ramp up' time, or whatever it's called - the period of time where the CO2 is on before the lights come on. It seems that to turn the CO2 on 1 hour before the lights come on is the typical method.

    I have been thinking about this a bit and I think it is something I have overlooked the importance of.

    I know that Tom has mentioned it's importance in the past.

    Sometimes (actually often) it takes a little while for thinks to sink into my head.... :)

    It seems that this CO2 lead time is the system's best shot at getting up to 30ppm. That would be correct? If the system is below 30ppm by the time the lights come on it's all downhill from there, the system will probably never make it...correct?

    So the aim is to get the system from, say, 0ppm to 30ppm, before the lights come on. For some not so heavily planted + lower light tanks, I can appreciate that 1 hour could be enough time for this to happen (i.e. the set diffusion/bubble rate to maintain the tank during the photoperiod will also be adequate to get the tank to 30ppm in an hour. But for more heavily planted + higher light tanks, is it not possible that 1 hour might in fact be too long (i.e. the set diffusion/bubble rate to maintain the tank during the photoperiod will get the tank to 30ppm much faster than an hour), thereby possibly stressing the fish etc?

    It almost seems that one needs to first set the required bubble rate to maintain the system at 30ppm during the photo period, and then tailor the duration of the CO2 lead time accordingly.

    It would also seem to me that people who can actually leave there CO2 'on' all night long (i.e. a very long CO2 lead time) must be nowhere near 30ppm by the time the lights come on??

    Am I making any sense? ;-)

    Scott.
     
  2. ibanezfrelon

    ibanezfrelon Guru Class Expert

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    I turn it on 2 hrs before the lights , 1st hour i release co2 at 50% buble rate and 1 hour before the lights i turn it up to max..
     
  3. detlef

    detlef Subscriber

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    Hi Scott and all,

    this issue got me thinking a lot lately too.....

    Why does Amano have very nice plant growth (and hardly any sign of algae) with CO2 diffusion only when lights are on? And why do the guys from CAU have equally well looking plants with CO2 injection 24/7 ?

    What about live stock when O2 is lowest (in the morning) and CO2 was started much earlier say 1 or 2 hrs before lights turn on? I have observed heavy and fast breathing in red neon tetras when I used "ramp/lead" times and heavy injection.

    What do plants really take in? Liquid (dissolved) carbon or the gaseous phase? Or both? Does CO2 really need to be dissolved (which of course takes time to reach a measurable amount of H2CO3 acid equivalent to say 30ppm of dissolved CO2) or do plants take it in as soon as the gas is bouncing around hitting the leave surface? If the latter is correct there should be no need to start injection using diffusers before lights come on. Right?

    Sorry, only questions no answers.


    Regards, Detlef
     
    #3 detlef, Jul 2, 2010
    Last edited by a moderator: Jul 2, 2010
  4. Oreo

    Oreo Guru Class Expert

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    For my aquarium I use a reactor method where 100% of my CO2 is disolved. There is no bubble mist in the tank. I have my CO2 turned up till the fish gasp and then turn it back just a bit till the fish are happy. Using a pH meter I use this reading as the CO2 set-point goal. It takes a 3 hr lead time for the pH meter to get ~close. But the pH continues to drop slowly from CO2 injection for the rest of the day till the CO2 turns off. My highest CO2 levels are at the end of the day. So I'm not really seeing what you are seeing.
     
  5. nipat

    nipat Guru Class Expert

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    One of my timers broke a few months ago, so I've been turning light and CO2 on at the same time
    for a while, haven't noticed difference.
     
  6. Tom Barr

    Tom Barr Founder
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    Most their tanks are very short of livestock fish..........far less than any of my tanks at home.
    Not much O2 demand, and if they have some fish, they are dainty easy, tolerant species regarding CO2.

    CAU rarely have breeding discus for example............ADA? Not sure if he's ever breed them in a planted tank, but I do not see why not either.
    Still, not a common scene curiously.........

    The other thing is the only ADA tanks I've measured with a light meter suggest pretty low relative PAR intensity.
    So CO2 demand is lower that most predict with their w/gal rules.

    They are also much more focused on gardening and scaping than most people who are in this hobby.
    They put a lot more effort and day to day care to get those tanks into that level of shape.

    I think this stress is temporary, and as long as it does not go on too long, fish are okay.
    Same with the day time in general, but we have the plants adding O2 also by the first 30-45 minutes also.

    Everything takes in/releases liquid CO2 and it degases and is released. Our bodies, the plant's organs etc.........they exist in a liquid phase.
    So no matter if the source is gas or liquid, the transistion to liquid must occur, same for O2 for that matter.

    I'd say about 5% of the CO2 we add makes it to the plant, the rest is lost.
    The CO2 gas vs the liquid phase is admittedly extremely difficult to measure directly.
    We can do indirect measures(growth rates over time, measure C in plant tissue, O2 levels over time with one liquid dissolved vs a microbubble method with the same pH/Kh/CO2 thermo coupling, IR reference cell etc)

    Me too mostly.
    The mist idea was just a simple method to blast the CO2 gas into the plant beds much like terrestrial systems, using a needle wheel, this seems to do this very well.
    The mist is barely noticable using the needle wheel also, much less so than the mazzei venturi.

    So having a power head is the biggest distraction in the tank, but they are far more stable/reliable than disc in terms of consistent CO2 delivery.
    I also think people that are skilled at observation of their plants have a better ability to slowly dose CO2 slow and progressively, than say many others.
    This experience cannot be discounted.

    CAU/Amano, myself, I think we are all pretty good at that, I have more fish however, plecos that also tend to need higher O2 ...or large Discus for clients so my tolerance is going to be less. Altums are pretty tolerant of CO2 BTW.
    I also think once the tank fills in and the plants dominate, the algae issues is extremely minor.

    There's a few things going on and they all play some role.

    Lower light is the biggy, fish that are highly tolerant of CO2 is another and less emphasis on fish in general, more of plants/design etc.....total nutrients is still high.
    They know what the plants should look like and are patient enough to slowly adjust/tweak CO2 to suit.

    I doubt they measure CO2 that much.
    I hardly do these days unless I want to get a precise reference when the tank is doing well.
    When the tank/s are not doing well, I know what's wrong.

    Regards,
    Tom Barr
     
  7. Tom Barr

    Tom Barr Founder
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    Here's like, the only know data that uses thermo couple CO2 meter and 15 min time ticks:

    [​IMG]

    A good CO2 system will ramp up the CO2 in 30-45 minutes tops.
    A poor system will take say 1-2 hours.

    Many that switched over to 24/7 I suspect have lower light and/or, they are the lower ramp up times, so they are just barely adding enough CO2 for the light period when doing 24/7 and not enough when doing only during the light phase.

    Plants suck up the CO2 mostly in the first 1/2 of the day, after about 6-8 hours, they are done(most species, many others will keep on growing and using CO2), many species will "close up" mostly fine needle stem plants, a few wider leaf species as well. Any plant that does this is done taking in light/CO2.

    So adding light after 8-9 hours is likely a waste. I've reduced the light time down to this level where most of them close up. The needle wheel adds more CO2 faster than any method, I suppose I could add CO2 15 minutes prior to lights on. But I'd rather not have another timer and mess with that.

    No lights/no CO2.
    I could tweak it a bit more I suppose, but I do not bother.
    Disc take another 5 minutes or so if good and clean, not old/cheapo clogged etc, or has check valve or solenoid issues etc. Needle wheel have positive suction, disc have backpressure, fine filters basically that can clog. I clean mine 2x a month really good.

    I've used cheapo brands of disc, they where hit or miss, most stink.
    They clogged too much, gave inconsistent mist. I went through 20 disc to get the 4 I now have that do okay. They change a fair amount before I clean then also.

    I'll be moving entirely to needle wheel methods sometime this summer.
    I like the disc visually, they are easy to see if the CO2 is being added correctly as I walk by, reactors/Needle wheel, this is harder to see.

    So there's a trade off.

    I guess a small disc and then mostly needle wheel is one method I use on one tank that gets around that.

    Regards,
    Tom Barr
     
  8. dutchy

    dutchy Plant Guru Team
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    Because O2 is at it's lowest in the morning, the MP40 switches on two hours before lights on. One hour before lights on the CO2 starts. pH is at 7 in the morning and 45 minutes later it's 6,3. Maybe I could do it even faster. I'm not afraid the system can't get to 40 ppm after lights on. If it can't, I think the system has a poor design. But what I can see is that very short after the lights are on the plants start to use a lot of CO2. I have two CO2 systems, and one is pH controlled. The first hours the pH controlled system is continiously on, later is starts to go to on/off mode. A poorly designed system could never cope with that if it starts when lights switch on.

    So I'd never want to risk a CO2 deficiency. Better be safe than sorry. Still it stays difficult to do it right. It took me two CO2 systems, 2 modified AM1000's and two 500GPH filters to get enough CO2 in my 180 gallon.

    I do the same as Tom does. As soon as the leaves are closed, lights switch off.

    The discussion should be about "why not" and not "why". ;)

    regards,
    dutchy
     
  9. Tom Barr

    Tom Barr Founder
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    I think I also have better luck with higher fish loads by over filtering, having high current etc than say CAU or Amano may.
    They say it(less fish stocking) helps focus more on the overall scape. Well, I like the look of more fish personally for my own tanks at home.

    Erik Olson from "The Krib" and family stopped by last week and they were amazed at the volume and vigor of my fish.

    I think the large water change sI do have been more about the fish than the plants, much like Discus breeders do.
    But this makes things good for plants and easier to control nutrients, the general concept is far far from my idea regarding EI and water changes.
    I juts took a normal habit that many aquarist already where using, and applied it to dosing ferts, instead of removing fish waste.
    Amano and CAU make use of large water changes as well, ADA's tap is about 0.5ppm PO4 also.

    Fish eat better, behave with more vitality when there's good current and ample O2.
    I'd suggets they also live much longer also, than the stressed lazy hardly swimming conditions that neglects the feeding and focused on scaping too much.

    Amano has admitted to killing fish with CO2, ask him.
    Many folks have.

    I think the CO2 error should be always 100% of time in favor of the fish's needs, not algae or plant growth(these can be addressed, you cannot bring.
    A good management goal and how best to get there with this in mind is the best management practice IME/IMO/in my ethical view point.

    CO2 is safe if used correctly.

    We see plenty of folks gassing fish, killing them or gasping them to top............now if this is not user error, mistakes, whatever you want to lavel it, I do not know what is.
    Then they tell me they are 100% sure that the CO2 is perfect/good, cannot be the issue.
    Right..........myself, CAU, Amano, everyone has issues with CO2.
    Get frigging use to it and try and resolve a better solution.

    No one is 100% on CO2, that is the one truth. Nutrients we can get pretty close to 100%, light? Well some could argue PUR vs PAR, but a decent meter can get us pretty close as well, at least 90% for most cases.
    They make a nice spect for the entire light range, but 3500$.
    I'm just not that interested in artificial light yet.



    Regards,
    Tom Barr
     
  10. scottward

    scottward Guru Class Expert

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    Thanks for the discussion guys, it is good reading.

    Tom, would it be a good idea for any of us who are switching our CO2 on 1 hour before to reduce this to 45 minutes? If, after reducing the lead up time, our tank starts to look worse, this would be a pretty good indication that we need to push the CO2 even higher?
     
  11. scottward

    scottward Guru Class Expert

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    I've been doing some more thinking about this...

    Let's say I accurately (i.e. electronically) measure the CO2 level in my tank and it's 0ppm. Then I start the CO2 injection into the tank and monitor the rising CO2 level. Let's say that after some experimentation, over several days perhaps, I find that at 5bps I can raise the tank from 0 to 30ppm in 45 minutes. Cool.

    So 5bps is now my bubble rate.

    Once the lights come on and the plants have their 10 hours or so of light, this 5bps might be insuffient to keep the CO2 level up around the 30ppm mark, it might be just right, or it might be too much such that by the end of the photoperiod the CO2 level starts to get dangerous.

    If, for example, the 5bps is not enough during the photoperiod, I cannot simply increase the bubble rate as this will also afftect the CO2 lead up. The fish may end up gasping (or dead) if I push the system further.

    It seems that if I did have to increase the bubble rate during the photo period, such as in this example, I would actually need to REDUCE the CO2 lead time.

    So my question now is, how is the 30-45 minute 'ideal' ramp up for a good system determined?

    How much is a good electronic CO2 meter?? I'm thinking if I had one my tank would be much better off as I could measure at various 'milestones' and get a very good understanding of what's going on with my tank!

    Scott.
     
  12. dutchy

    dutchy Plant Guru Team
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    That's exactly why I did it like this: Two CO2 systems. One of them is pH controlled. The one that is not pH controlled has a basic bubble rate, let's say 5 bps. Both systems are on in the morning to get the desired CO2 level within 1 hour. Easy to do with two systems. When the desired CO2 level is reached, the pH controlled system will switch off. The basic bubble rate system will keep the desired level but is not set high enough to overdose CO2. As soon as plants start to use a lot of CO2 or grow over time and space the pH controlled system will switch on and compensate.

    I don't care very much what the number is on the pH controller, it's purely set on what my fish can handle. The decision on two systems was basically made on tank size and to get CO2 in to both sides of the tank.

    regards,
    dutchy
     
  13. scottward

    scottward Guru Class Expert

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    I have seen the photos of your tank Dutchy, it looks fantastic, nice work!

    The two systems idea sounds like a good one, although couldn't you achieve essentially the same thing using the single pH controlled system?

    Couldn't you just set your CO2 bubble rate so that in the first 30 minutes you hit the jackpot, note what the pH is at this point, and then ensure your pH controller keeps thumping the CO2 in accordingly so it stays there?

    It's interesting that you are having good success with the pH controlled system. At one point I thought this was the way to go, and I thought about buying such a system, but I heard so many things going against them as well. I might shoot you some questions about it on your thread.
     
  14. dutchy

    dutchy Plant Guru Team
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    Thnx Scott. :)

    I tried , but it didn't work with two AM1000's. (Or maybe I'm not smart enough :) ) So I decided to use two systems, which also gave me the option to use two CO2 cylinders. Anyway the capacity of each system is enough to supply the tank with enough CO2. Redundancy is a good thing. :)

    That would be no problem. It's just what you want.

    I think it's a good thing, if you use it right. if you set your CO2 level by the pH number on the display, you could be a mile off. I set the CO2 level according what the fish can take, not the pH on the display.
    If I would do that, I would have a serious CO2 difficiency.

    Hope this helps,
    Regards,
    dutchy
     
  15. Tom Barr

    Tom Barr Founder
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    It can work with a single system, eg a needle wheel and a good sized pump, more flow through the CO2 system.........the faster response times and more effective it is.

    You should be able to ramp the CO2 up and dial things in well without a pH controllers, but using one as a relative measure, not bad either.
    I'm not a fan, mostly because the CO2 changes a lot in the tank in different areas, so the issue is one of temporal changes but also spacial changes and plant species are different in their CO2 demands/uptakes also.


    so where you take these pH readings is a big issue, and the pH seems not to be as responsive as the thermocouples.



    Regards,
    Tom Barr
     
  16. dutchy

    dutchy Plant Guru Team
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    I used needle wheel for some time. Although it worked well, it seemed to have some disadvantages. I was clearly using much more CO2, because the bubble size was bigger. Also the constant churning inside the impeller wasn't very nice.

    But how can you provide for CO2 changes due to temporal changes and various CO2 demands/uptakes with a non pH controlled system?

    Let's say that you have a fixed bubble rate, which will give you a certain ppm of CO2. At the moment the demand increases, like 1 hour after lights on, the non pH system could be the cause of a CO2 deficiency. It will give no more than the set bubble rate. I can turn the valve wide open and that way it has a lot of capacity without the risk of gassing fish. Also as plants grow over space and time, the uptake will increase. If you don't compensate for that, a deficiency will occur. That way todays sufficiency will be next months deficiency. The pH contolled system will compensate automatically, within limits of course. Maybe it's not very responsive, but it will respond. Better than nothing ;)

    I agree that placement of the sensor is critical. My pH sensor is in a corner of the tank, 10 inch BEHIND one of the CO2 outlets. So the CO2 enriched water goes the opposite way in relation to the sensors' position. So every system has it's limitations, but I think they are more caused by the user than by the system itself.

    regards,
    dutchy
     
    #16 dutchy, Jul 9, 2010
    Last edited by a moderator: Jul 9, 2010
  17. hbosman

    hbosman Guru Class Expert

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    Tom, you run one timer for lights and CO2? I was looking to simplify but not if it will cause algae issues.
     
  18. shoggoth43

    shoggoth43 Lifetime Charter Member
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    A single timer for both will work. While it won't be ideal for when you first start in the morning, it has proven adequate over time. You may find that you waste some CO2 later at night, especially if you have plants that close up when done and there's still time left before lights out. Alternately, if you have enough surface turnover/gas exchange you can always just let it run without CO2 and see what happens. I'm getting ok growth on mine after I finally discovered my bubble counter had shattered, but I'll still be putting it back into play.

    -
    S
     
  19. scottward

    scottward Guru Class Expert

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    Hmmm. This has got me thinking. I, like a lot of people turn my CO2 on 1 hour before the lights come on (just because that seems to be 'the go'). If the plants take 35-40 minutes or so to ramp up their CO2 usage to the max, this same window of time should allow the CO2 to build up adequately..shouldn't it? So it would seem to me that perhaps the usage of a seperate timer would assist only in switching the CO2 off a bit earlier than the lights go out?

    Maybe myself, and a whole heap of other people, are really just wasting CO2 running it for 1 hour before lights on?

    So Tom you just have a simple lights on - CO2 on; light off - CO2 off setup? The key is really in having a responsive CO2 enrichment method...making the concept of 'CO2 lead time' redundant?

    For setups that have a less responsive CO2 enrichment method, it would seem to me that CO2 would plateu at a lower level anyway (Boyle's law?), or they would have to thump their system with more gas to get the required response time (albeit inefficiently).

    So measuring pH, using an electronic meter, from a set point in the aquarium, could be a good way to obtain data to provide some feedback as to how responsive the CO2 enrichment method is? I'm thinking of buying an electronic pH meter - are they all created equal or would a good chemical pH test with liquid references (i.e. not a colour chart) be pretty good also and much cheaper?
     
  20. shoggoth43

    shoggoth43 Lifetime Charter Member
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    Electronic probe would allow for easier monitoring in different locations in the tank. Depending on probe design you might be able to take measurements at different depths.

    The chemical one will allow for some general relative measurements. OTOH, so will a drop checker, just not quite so immediate a response.

    -
    S
     
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