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Dialling in the CO2 injection Rate and CO2 Profiles

erwin123

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dialing CO2 can be simplified if you keep your equipment and layout simple like in the 2hr aquarist setup above. Essentially there are only 2 variables:
(1) When to turn on/off CO2
(2) How much CO2.

And frankly, there is only so much you can do with those 2 variables. After dialing in 1.5bps into my Qanvee diffuser (different bubble counters have different bubble sizes) and starting CO2 3 hours before lights on, my focus had to shift to getting adequate flow of CO2 enriched water to the substrate level. which is probably the subject matter of another guide :)
 

Yugang

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@Zeus. perhaps one edit suggestion to your great post - the importance of keeping surface agitation stable and at a gentle level.

Nearly all the CO2 that we inject will end up being outgassed at the surface. Only a minor part (probably <20%) get's absorbed by plants in most tanks.
When starting the dialling in process with a reasonable surface agitation, for sufficient gas exchange as mentioned, it is very important to not change this surface flow during or after the described process. 10% change in outgassing at the surface, due to changed flow from spray bars, lily pipe, etc, will have an equivalent effect as perhaps 10% injection change.

Surface agitation is often overlooked, a major factor, hence my addition
 

Zeus.

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PH controllers are always overlooked.

All my problems disappeared once I got mine. Does away with the endless fiddling - set target PH, open the valve to a sensible position. Job done. Accurate too, holds target +/- 0.03

Which one do you have?

I started off with a pH controller myself which made the whole process easy as you said. It wasn't cheap and I found the one I had fluctuated a little with the pH over a range up and down all the photo period. The probes also need regular calibration to prevent pH drift. I found setting the injection gave me a more stable CO2 level and no calibration was need. Later on I integrated the pH controller into my PLC. So when the target pH was reached a signal was sent to the PLC which recorded the time it took and adjusted the pre lights CO2 on time. The PLC with duel solenoids and CO2 injection also made the whole process every easy. I use to have the two injectors on for the pH drop, then when I hit the target pH one went off and the other maintain the stable pH level. Was even able to drop the pH in a 500litre tank in about 20 mins.
 

Zeus.

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If you hit 20 ppm CO2 at the start of photoperiod (just pretend that's what they need), and then you hit 30 ppm later in the photoperiod, then this is perfectly fine and the CO2 need not be "stable" at 20. This would be observed with a pH at lights on and a lower pH later. Chances are your fish would demonstrate lethargy and turning off CO2 before lights off would be a natural accomodation for your tank.
This would be not advisable based on the science behind having a stable pH Stable CO2 - What does it mean exactly? Clive covers why we need a stable pH
 

Zeus.

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@Zeus. perhaps one edit suggestion to your great post - the importance of keeping surface agitation stable and at a gentle level.

Nearly all the CO2 that we inject will end up being outgassed at the surface. Only a minor part (probably <20%) get's absorbed by plants in most tanks.
When starting the dialling in process with a reasonable surface agitation, for sufficient gas exchange as mentioned, it is very important to not change this surface flow during or after the described process. 10% change in outgassing at the surface, due to changed flow from spray bars, lily pipe, etc, will have an equivalent effect as perhaps 10% injection change.

Surface agitation is often overlooked, a major factor, hence my addition
I do mention it briefly, but will expand on it a little more as you suggested. Thanks for the feedback, it all helps then we can have a single opening post that covers all the major details which folk new to CO2 need to be aware off :thumbup:
 

Sdogg

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Which one do you have?

I started off with a pH controller myself which made the whole process easy as you said. It wasn't cheap and I found the one I had fluctuated a little with the pH over a range up and down all the photo period. The probes also need regular calibration to prevent pH drift. I found setting the injection gave me a more stable CO2 level and no calibration was need. Later on I integrated the pH controller into my PLC. So when the target pH was reached a signal was sent to the PLC which recorded the time it took and adjusted the pre lights CO2 on time. The PLC with duel solenoids and CO2 injection also made the whole process every easy. I use to have the two injectors on for the pH drop, then when I hit the target pH one went off and the other maintain the stable pH level. Was even able to drop the pH in a 500litre tank in about 20 mins.
I have the UP PH controller

It hardly drifts for me. I recalibrate it every month just for good practice and it's never been off by more than 0.05 from the buffer solution.

I swear by mine.
 

Yugang

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I have the UP PH controller

It hardly drifts for me. I recalibrate it every month just for good practice and it's never been off by more than 0.05 from the buffer solution.

I swear by mine.
This is also my experience.

My calibration routine was to take some water after weekly 60% water change (mostly degassed already), let it further degas for one night and dip the pH probe in, just to be sure everything is ok.
Mostly I would find that calibration still good and find same pH value again, but only if needed adjust the pH 7 calibration. Don't worry about pH 4, the slope. Only monthly, or even with longer interval, check calibration with both pH 7 and pH 4 buffers. After some time, everything as expected, checking starts to be boring and allow longer intervals.

If you're friendly with your pH probe, understand what it does and needs, it is a great tool.
 

foxfish

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I have the UP PH controller

It hardly drifts for me. I recalibrate it every month just for good practice and it's never been off by more than 0.05 from the buffer solution.

I swear by mine.
That is interesting as you must be one of very few people who have posted on this forum quoting total success using a PH controller!
PH controllers have notoriously not worked for the majority of people who have tried them ….at least according to the post recorded on this forum.
So this may be a big break for others to follow, can you give us more details about how you run yours?
 

JoshP12

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Just to reiterate -- it is a good approach to get stable co2 and it will work. But we don't need it -- acknowledge here most hobbyist just want it to work - but for those who question why Barr and ADA, FIlpe O, and others don’t worry about this (turn co2 with lights on - contradicts stability) it is due to what I said above (and more specifically a non-uniform co2 demand - there’s other stuff that we need not get into on this thread too).
This would be not advisable based on the science behind having a stable pH Stable CO2 - What does it mean exactly? Clive covers why we need a stable pH
 

Yugang

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That is interesting as you must be one of very few people who have posted on this forum quoting total success using a PH controller!
Well, perhaps this is a sign of
scientifically immature
Just check #34 of @GreggZ journal. Some use pH controller and are extremely successfull with it. CO2 controllers work for those who understand and know how to operate.

We all seem to accept pH profiling, complementary to drop checker, but suddenly see many risks using pH to control CO2.

If you're friendly with your pH probe, understand what it does and needs, it is a great tool.
 

MarcusA

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I've been measuring my CO2 without degassing it first. I have noticed that the pH value in the morning varies somewhat. This week it has ranged from 7.87 (the day after a water change) to 7.64. Would degassing it get rid of this variance? Is it caused by lingering CO2 from the night before?
 

JoshP12

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I've been measuring my CO2 without degassing it first. I have noticed that the pH value in the morning varies somewhat. This week it has ranged from 7.87 (the day after a water change) to 7.64. Would degassing it get rid of this variance? Is it caused by lingering CO2 from the night before?
It is (plants breathe - releasing co2 - but won’t be using up that co2 via photosynthesis).

Yep can take your drop from degass (roughly 3ppm co2 residual in water after degassing).

Can also guesstimate it with a somewhat reliable KH … find the 3ish ppm point oh ph/KH chart … should be close “enough” for the drop … lethargic fish will alarm you if you overshoot.
 

GreggZ

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Well, perhaps this is a sign of

Just check #34 of @GreggZ journal. Some use pH controller and are extremely successfull with it. CO2 controllers work for those who understand and know how to operate.

We all seem to accept pH profiling, complementary to drop checker, but suddenly see many risks using pH to control CO2.
Yep I've been using a pH controller for many years and wouldn't be without it. It makes it easy to keep a consistent CO2 level, and takes a lot of the guess work out of the process. Set it and forget it. What could be easier? I know every day my pH drop is in the 1.3 to 1.4 range all day long. Doesn't matter how much plant mass there is. Doesn't matter how much surface agitation there is. Doesn't matter if a needle valve drifts. Trust me there are numerous ways to get CO2 wrong.

And everyone quotes "30 ppm" CO2 is somehow a magic number. The problem is you really have no idea what your CO2 ppm is without expensive test equipment. There are other things affecting pH in our tanks besides CO2. According to the calculators my 1.4 pH drop is about 100 ppm CO2? Is it really? Unlikely. But matters little. A 1.4 drop is where my plants are at peak health and my Rainbows don't show any stress.

As to drop checkers, it's just a liquid pH test kit. And liquid pH test kits can be off quite a bit and IMO are not accurate enough for our purposes. But like everything else in this hobby much depends on your ambitions and the type of tank you keep. As you turn up the light and add loads of stems, getting CO2 dialed in becomes more important. For lower energy tanks, some is better than none and it's not quite as important.

For those who suggest less CO2 is somehow better I don't know where they get that notion. Getting CO2 optimized is easily the best thing one can do plant health in a high tech tank. Barr's been saying it for years and he's right. And by the way Barr has used pH controllers many times. He uses them on his customers tanks as he's not there to constantly dial it in for them.

There is one caveat. If your dKH is not stable, then a pH controller may not be the best option. As dKH changes so does fully degassed pH.
 

Hanuman

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For those who suggest less CO2 is somehow better I don't know where they get that notion.
I think you are reading that in a different way. What I understand is that CO2 levels lower than the "standard" 30ppm baseline that has been repeated ceremoniously for years, can also work. Reality is that plants will adapt and grow accordingly to what is available. It's all a matter of plant selection and CO2 consistency. You can get away with lower CO2. That's what low/medium tech tanks do and plants are fine as well. You might not have the full spectrum of plant selection and coloration you have with high intensity tanks, but it doesn't mean you can't grow plants perfectly healthy.
 

Yugang

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Yep I've been using a pH controller for many years and wouldn't be without it. It makes it easy to keep a consistent CO2 level, and takes a lot of the guess work out of the process. Set it and forget it. What could be easier? I know every day my pH drop is in the 1.3 to 1.4 range all day long. Doesn't matter how much plant mass there is. Doesn't matter how much surface agitation there is. Doesn't matter if a needle valve drifts
Barr has used pH controllers many times. He uses them on his customers tanks as he's not there to constantly dial it in for them.

I fully subscribe to this, once one knows to use pH probes it makes CO2 management very easy indeed. The main problem with pH probes in my opinion is reputation and lack of knowledge. All the mastery that @Zeus. describes so well in the opening post, taking much time and effort, is then virtually redundant.

As you say,
There is one caveat. If your dKH is not stable
there is a big chance for trouble. As described in a previous post, I used to do a quick calibration check after each water change, knowing that dKH variation within one week in my tank were extremely small. After some time, even this weekly calibration checks were not usefull anymore for me, but they may be for people with an KH inconstent water suppply at WC.

After several happy years with my pH/CO2 controller I stopped using it. The controller switches the solenoid off when target is reached, then on again when pH has drifted 0.1 pH higher. When on, you inject a wave of relatively highly injected water in the tank, leading to localised CO2 inhomogeneities for the plants. This effect can be minimised by setting a lower bubble rate, but the downside is that it does not longer allow for the fast ramp up that is possible with pH/CO2 controllers.

PS. CO2 dream machine builds on the benefits of pH/CO2 controllers, but takes it one step further with new benefits. How much more productive could that discussion have been with your above input, @GreggZ , and reference to other champions like Tom Barr :) Dream Machine is sound from technical perspective, hope that somebody has already picked it up. I have found a more powerful concept however, simpler, cheaper and can probably be built by a hobbyist in a garage box. Still contemplating if/how to share for the hobby;)
 

Hanuman

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What about the argument that measuring the pH drop is inaccurate to the point of worthlessness because the amount of pH in the atmosphere varies?
It is discussed in detail here: pH Drop CO2 accuracy
I wouldn't go that far. It is inaccurate indeed just like the drop checker is as well. But those are the only 2 ways we have of extrapolating CO2 content. They are simply guidelines. As for the PH in the environment I suppose you meant CO2. That is technically correct but I don't think most of the time we have more than 500/800ppm around. If you have above 1000ppm something is not right or you live in a closed environment and I think that's not the case for most people having tanks. Does it occur in some people home, surely but in a daily average your atmospheric CO2 would probably be sub 1000ppm.
 

MarcusA

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I wouldn't go that far. It is inaccurate indeed just like the drop checker is as well. But those are the only 2 ways we have of extrapolating CO2 content. They are simply guidelines. As for the PH in the environment I suppose you meant CO2. That is technically correct but I don't think most of the time we have more than 500/800ppm around. If you have above 1000ppm something is not right or you live in a closed environment and I think that's not the case for most people having tanks. Does it occur in some people home, surely but in a daily average your atmospheric CO2 would probably be sub 1000ppm.

Yeah, thank you. When I said pH in the atmosphere, I meant CO2 in the atmosphere. I worry because my tank is in my bedroom, and I work from home, often with the door closed by necessity, so I'm in there a good 16 hours a day, pumping out CO2. I'm thinking of a getting a CO2 air monitor, but I can't figure out if there any affordable and accurate ones available.

Would it be possible to measure the CO2 in a room by measuring the pH of 7.0 reference solution after its been sitting in an open container in the room for a while?
 

Hanuman

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I worry because my tank is in my bedroom, and I work from home, often with the door closed by necessity, so I'm in there a good 16 hours a day, pumping out CO2. I'm thinking of a getting a CO2 air monitor, but I can't figure out if there any affordable and accurate ones available.
Your atmospheric CO2 is probably high in that case unless you have some aeration going on or big gaps between door and frame. For the monitor, have a read from this post onward.
Would it be possible to measure the CO2 in a room by measuring the pH of 7.0 reference solution after its been sitting in an open container in the room for a while?
You'd probably better off getting a CO2 monitor.
 

GreggZ

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What about the argument that measuring the pH drop is inaccurate to the point of worthlessness because the amount of pH in the atmosphere varies?
It is discussed in detail here: pH Drop CO2 accuracy
Ha a blast from the past my old friend Edward.

I can tell you this. I know a LOT of people in the hobby. I can pretty much predict what their degassed pH will be based on their dKH. It's usually right about 3 ppm to 4 ppm. It's been the same for decades, and it's the same around the world. If you don't get that number, then usually there is something wrong with your methodology, or something else is affecting your pH (ex. sodium hydroxide).
 
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