# Dialling in the CO2 injection Rate and CO2 Profiles



## Zeus.

*Why do we need a stable Carbon Dioxide (CO2) level?*
A stable Carbon Dioxide (CO2) level or concentration is key to successfully growing plants in a CO2 injected tank. The CO2 concentration needs to be stable throughout the photoperiod, usually anything from 6 to 8 hours long, and consistent from one day to the next. If the CO2 level is not stable during this period, plants will have to constantly adapt and may not grow as well. A fluctuating CO2 concentration may also give algae an advantage and it could start to become a problem.

Stabilising CO2 during the photoperiod can be tricky and time consuming, and can sometimes take weeks of trial and error, especially for folk new to CO2 injection. Also key to success is good water flow. This is often overlooked but is essential to distribute CO2 evenly throughout the tank.  CO2 travels 10,000 times slower in water than in air, so without good flow CO2 concentration will not be the same throughout the tank. Plants waving gently in the flow is a good indicator that it is adequate. Good surface agitation is also essential. This ensures adequate levels of gas exchange and helps to keep the tank water oxygenated.

*What level of CO2 to aim for?*
Many folk aim for a CO2 concentration of 30ppm. This is regarded as the upper safe limit for livestock. A lower CO2 concentration than 30ppm CO2 can also greatly benefit plants and is perhaps kinder to livestock, so don’t feel the need to hit the 30ppm mark. When tank water has 30ppm of CO2, the pH will be approximately 1.0 unit lower than it was before CO2 was injected. To find a tank’s CO2 level or baseline before injection starts, take a clean glass of tank water and leave it at room temp for 24 hrs after which take a pH reading. This will be the baseline or degassed pH of your tank water. For example, if the pH is 7.2 after fully degassing, and your target CO2 concentration is 30ppm then the target pH will be 6.2.

*Watch your fish when Injecting CO2*
It is best to adjust CO2 levels before adding any livestock to avoid accidentally stressing fish and other aquatic critters. If this is not possible it is essential to keep a close eye on your fish and shrimp etc when first injecting CO2 especially if you are new to the concept. Watch for any signs of abnormal behaviour. If the fish come to the surface and start gasping for air or show any other signs of distress, stop CO2 injection immediately. If this happens a large water change will be necessary as a temporary fix to reduce CO2 concentration and hopefully introduce more oxygen. Next check your equipment and don’t start CO2 injection again until you are confident the cause has been eliminated. If you are unable to get to the bottom of the problem seek advice or guidance, never be afraid to ask.

*Injecting CO2*
After starting to inject CO2 the pH of the tank water will drop quickly at first, then slowly until it reaches equilibrium with CO2 uptake by plants and CO2 loss from the water surface. If the injection rate is too high, you will overshoot your target CO2/pH which could be fatal to the tanks inhabitants so small steps at first are essential to avoid this. If the injection rate is too low, your tank water may take many hours to reach the target CO2 concentration and may not hold that concentration and remain stable once the lights come on. It’s often a case of trial and error, taking the greatest care to get it right especially when livestock is present.

*Drop Checker (DC)*
A drop Checker (DC) is a great tool for checking the concentration of CO2 in tank water. A working DC is filled with an indicator solution, usually a reagent in deionised water calibrated to a value of 4dkH. This solution changes colour according to the concentration of CO2. The colour will change from blue when tank water is fully degassed of CO2, to lime green when tank water has reached a CO2 concentration of 30ppm. DC’s can often change colour slowly; the rate varies with design and can take unto 2hrs. A DC can be used by itself to gauge CO2 concentration, however for the purposes of establishing a stable CO2 concentration it’s easier to use the combination of a pH profile and a DC

For further information on measurement using a drop checker, see Clive’s excellent article linked below


			CO2 Measurement Using A Drop Checker
		







*Time it takes to get your target CO2 level*
The time it takes to reach a CO2 concentration of 30ppm varies with tank size and injection method. About 2hrs is normal for a 50 litre tank, but bigger tanks can take 4 to 5 hours plus.

*Doing a pH profile*
Doing a pH profile is a great way to achieve a stable CO2 concentration and is relatively simple to do, ‘if’ a little time consuming. Firstly, decide on your target CO2 level. Then find the baseline or degassed pH of your tank water as outlined above under the heading - What level of CO2 to aim for. Set the injection rate, or Bubbles Per Second (BPS) using a bubble counter, to a suitable level for your tanks size and CO2 setup. Take the pH of the tank water as CO2 injection starts or just before.

Thereafter, take a pH reading every 30 mins and note it down. As the pH change slows down start to take the pH a little more often. If the pH drops more than 1.0 unit reduce the injection rate (BPS). If it is taking too long to get the desired pH drop increase the BPS. Once the target pH is reached, turn the lights on, then keep taking the pH every 30 mins, repeating the BPS adjustment to keep the pH as stable as possible. After 4 to 5 hours of lights on turn the CO2 off and call it a day.

Next day take the pH as CO2 comes on and thereafter every 30 mins and note the time. As the target pH is reached turn the lights on and again note the time. Some fine tuning will probably still be needed to get a stable pH (I personally call it stable when there is less than 0.1 pH drift from lights on till CO2 off). So it’s a case of ‘rinse repeat’; check the pH and adjust BPS if required to suit, until you have a stable pH from lights on and all the way through to lights off. Then the hard work is over. DO NOT adjust your BPS rate again to try and get the pH to drop faster, it is not possible. The time it takes is the time it takes. You will have already got this time noted down. It may be 2hrs it may be 4 to 5hrs with bigger tanks. The length of time a pH drop takes is always worth a final check. You will already have a rough idea from the previous days pH profiling but some further fine tuning may be required.

The whole process can take days or even weeks to perfect, especially if you need to increase the water flow to ensure adequate CO2 distribution throughout the tank, or to increase surface agitation and therefore gas exchange. Other commitments, such as work and household chores, can interfere with the process so make sure you have at least a few days free to start with, any distraction may prove fatal to fish and other aquarium livestock, again another reason why it’s best to dial CO2 in before adding livestock.

*If in doubt ask*
Finally, there’s no such thing as a stupid question, especially where CO2 injection and the health of fish and other livestock is concerned. So if in doubt always ask. There are many experienced and knowledgeable members who will be only too happy to help.

Zeus.

Other threads/post to read for more detail- (please post thread details of threads/post you have found useful)

Stable CO2 - What does it mean exactly? The science behind having a stable CO2 level
Using a pH controller - Pros and cons of using a pH controller to control your CO2 levels
CO2 Used data base - gives an idea of how much CO2 tanks have used

Thanks to @Tim Harrison for helping in the making of this post/summary. Special thanks to @ceg4048 ( UKAPS CO2 Guru) for all his words of wisdom and 'wit' here at UKAPS over the years. Plus to all the members who have helped me with CO2 over the years


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## seedoubleyou

Thanks to you for taking the time.


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## JacksonL

Think this will help a lot of people. It can be a confusing process at first.


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## Andy Pierce

Great post!  You might consider adding under the *Watch your fish when Injecting CO2* heading that if things start going badly wrong an emergency big water change is a quick temporary fix.


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## Garuf

Zeus. said:


> A lower CO2 concentration can also greatly benefit plants


…what?


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## Garuf

Ps. That’s not me blahblahblahblah posting. This is genuinely news to me.


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## Zeus.

Andy Pierce said:


> if things start going badly wrong an emergency big water change is a quick temporary fix.





Garuf said:


> …what?


Lower than 30ppm CO2, say 20 ppm CO2 or 15ppm CO2 or even lower  I have edited fist post


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## John q

Brilliant and much needed post @Zeus.  Finally there's a sticky where folks can be guided to when they're struggling to dial in co2.  
Very easy to read and understand, kudos to you mate 👍


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## Garuf

Zeus. said:


> Lower than 30ppm CO2, say 20 ppm CO2 or 15ppm CO2 or even lower  I have edited fist post


But how is that good for plants? Steer me to some reading.


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## Zeus.

John q said:


> Brilliant and much needed post @Zeus.  Finally there's a sticky where folks can be guided to when they're struggling to dial in co2.
> Very easy to read and understand, kudos to you mate 👍


Thank you , The aim was to make it as concise as possible, without scientific terms, avoiding great detail and easy to follow/repeat.


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## Tim Harrison

Garuf said:


> But how is that good for plants? Steer me to some reading.


It’s nothing profound it just means that plants will benefit from some CO2 rather than none at all. But I guess it’s always best  to qualify that statement. It’s simply a question of choosing the right plants if you intend to inject just enough to turn the drop check green rather than lime green, for instance. Take George’s slow burner for example.

Thread 'NA 65cm - Slow Burner'
NA 65cm - Slow Burner


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## Zeus.

Garuf said:


> But how is that good for plants? Steer me to some reading.


The Lazy Asian Biotope 400litre tank and 1 BPS 24/7 Just boosting the CO2 level a little. 
There's quite a few Journals where low levels of CO2 have been used


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## Garuf

Okay, that was the needed clarification because I was here thinking I’d missed something while I was away but really the caveat was “provided you meet your selected plants minimum co2 threshold/demand”. Or am I still reading you wrong?


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## Tim Harrison

Garuf said:


> the caveat was “provided you meet your selected plants minimum co2 threshold/demand”


Yes, that’s about it


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## john6

@Zeus. Brilliant write up, plain and simple, makes co2 injection not as daunting as it first appears, its answered most of my questions i had regarding co2 injection and has given me the confidence to go ahead with injection when i set up my new tank.
Many thanks for the time and effort.


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## Sdogg

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


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## Yugang

Thank you so much for this article @Zeus.

It continues to amaze me how traditional CO2 management, after several decades, is still unnecessarily complicated and scientifically immature.  Both new and experienced users struggle with what should be a standardized and well documented part of the hobby, just like fertilization or filtration.

I am wondering, what would be the best way to proceed with another idea, outperforming "CO2 dream machine",  making CO2 management much easier and much better? This forum works for having fun with other hobbyists, constructive discussion and progress, some technical aspects -- so not sure yet .

Do not want to derail this valuable thread, so may take my idea  some time later to a new thread on CO2.


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## JoshP12

Firstly, thank you for taking the time to write this Zeus.

If I may:


Zeus. said:


> *Why do we need a stable Carbon Dioxide (CO2) level?*
> A stable Carbon Dioxide (CO2) level or concentration is key to successfully growing plants in a CO2 injected tank. The CO2 concentration needs to be stable throughout the photoperiod,


Suppose plants need 20ppm of CO2 to show no deficiency (this statement is rediculous since the demand is not uniform throughout the period, but I think many will understand what we mean).

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.

I just wanted to share that example illustrating one case where it need not be stable (up to error with pH testing) -- any absolute fluctuations will wreak havoc certainly -- but the example above obeys Leidbig's and many people run their tanks as such.

In my eyes, stability is a _good _guideline for the following: if you hit 15ppm at lights on and then hit 25 ppm later, this is a huge issue (given my assumption above that 20ppm is what is needed). And at some point the pH drop will flatten out ... so it makes sense just to turn it on 30 minutes earlier (for example) and go from there.

Optimization of CO2 implementation is whole other discussion. But again thanks for drafting this.

Josh


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## Yugang

JoshP12 said:


> 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 is not the consensus in the hobby. Plants adapt to a CO2 level, and need time and energy to adapt to a higher or lower level. Stability during photoperiod is key.


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## JoshP12

Yugang said:


> This is not the consensus in the hobby. Plants adapt to a CO2 level, and need time and energy to adapt to a higher or lower level. Stability during photoperiod is key.


Certainly not out to start a debate. Apologies.


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## erwin123

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


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## Yugang

@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


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## Zeus.

Sdogg said:


> 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.


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## Zeus.

JoshP12 said:


> 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


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## Zeus.

Yugang said:


> @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


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## Sdogg

Zeus. said:


> 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








						WEIPRO pH CO2 Controller for Planted Aquariums
					

Using the pH Controller you can put your CO2 deployment on auto-pilot, and only dose CO2 into your aquarium as and when it's needed.




					www.co2supermarket.co.uk
				




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.


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## Yugang

Sdogg said:


> I have the UP PH controller
> 
> 
> 
> 
> 
> 
> 
> 
> WEIPRO pH CO2 Controller for Planted Aquariums
> 
> 
> Using the pH Controller you can put your CO2 deployment on auto-pilot, and only dose CO2 into your aquarium as and when it's needed.
> 
> 
> 
> 
> www.co2supermarket.co.uk
> 
> 
> 
> 
> 
> 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.


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## foxfish

Sdogg said:


> I have the UP PH controller
> 
> 
> 
> 
> 
> 
> 
> 
> WEIPRO pH CO2 Controller for Planted Aquariums
> 
> 
> Using the pH Controller you can put your CO2 deployment on auto-pilot, and only dose CO2 into your aquarium as and when it's needed.
> 
> 
> 
> 
> www.co2supermarket.co.uk
> 
> 
> 
> 
> 
> 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?


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## JoshP12

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).


Zeus. said:


> 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








						Rubisco concentration light dependent?
					

Hi all,  So, I've been thinking :oops:. I recall reading that the argument for stable CO2 during photoperiod was because of the Rubisco concentration in a plant. In other words, getting a stable CO2 is the key to match your light.  If light drives CO2 uptake, and stability of CO2 is needed for...



					www.ukaps.org


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## Yugang

foxfish said:


> 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


Yugang said:


> 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.



Yugang said:


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


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## MarcusA

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?


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## JoshP12

MarcusA said:


> 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.


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## GreggZ

Yugang said:


> 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.


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## Hanuman

GreggZ said:


> 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.


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## MarcusA

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


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## Yugang

GreggZ said:


> 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





GreggZ said:


> 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, 


GreggZ said:


> 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


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## Hanuman

MarcusA said:


> 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.


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## MarcusA

Hanuman said:


> 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?


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## Hanuman

MarcusA said:


> 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.


MarcusA said:


> 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

MarcusA said:


> 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).


----------



## MarcusA

@Hanuman , what do you think of this idea: using a basic NDIR CO2 monitor to check CO2 levels in water by placing the monitor in a closed container with some outdoor air and some tank water at the bottom and allowing an equilibrium to become established between the air and water ala Henry's Law. Sort of like a giant drop checker.

@GreggZ, but don't CO2 levels vary a lot indoors? I'm still trying to get a grasp of how all this works.


----------



## JoshP12

@MarcusA 

You have it figured out. Although it is this minutia that allows us to truly understand what is happening, the impact on obtaining an arbitrary drop to some magic number is negligible. 

Is there a flaw in taking a 1.0 pH drop from degassed water with an air stone in your living room? Absolutely. But … it’s all estimates.


----------



## GreggZ

MarcusA said:


> @GreggZ, but don't CO2 levels vary a lot indoors? I'm still trying to get a grasp of how all this works.


Don't over think it. In the end the best level is one where plants are happy and fish are not affected. Here's a rant about CO2 measurement that I wrote in a thread a while back. Like I said before there are loads of ways to get CO2 wrong.

_Folks will often list tank parameters and say their CO2 is at 30 ppm. But is it? Best answer is “maybe”.

There are loads of ways to introduce errors into that equation. Let’s start with measuring dKH. Let’s take an example where someone measures their dKH at 5 and measures their fully degassed pH at 7.6. That would indicate a CO2 concentration of 3.78 which would be reasonable at equilibrium with the atmosphere. So they drop pH to 6.6 and claim they have 30 ppm CO2. The first mistake is that fully degassed water already has some CO2 in it so that actually calculates to 37.8 CO2 ppm..

But let’s say their measurement is off. 99% of folks use a liquid drop kit to measure dKH. If the true dKH is actually 5.7 CO2 would now calculate to 43.09. If the true dKH is 4.1 then CO2 concentration is 31 ppm. Either would be easy to do as we are not measuring down to tenths.

So there’s one variable that can have an effect on how we report CO2 concentration. Next is the methodology of measuring pH. Some folks use test strips or liquid kits that can be off by quite a bit. Using the same example above let’s say that that instead that instead of degassed pH at 7.6 it’s really 7.4 and instead of dropping to 6.6 it’s really 6.8. This is extremely easy to do when using a test kit and deciphering shades of color. Now CO2 concentration would calculate to 23.85.

And it’s even true when using calibrated probes. A long time ago I tested 3 different calibrated pen type pH meters against each other. They all gave different readings. Next best is a higher quality BNC connected type probe. More accurate but still not lab grade equipment.

So the point is many times the reality is that measuring pH drop and dKH are a garbage in garbage out methodology. And when you combine errors in both readings you can begin to see how two people testing the same water could come to wildly different conclusions about their CO2 ppm. So when someone says my CO2 is at 30 ppm, most times they really have no idea if that is true or not.

Then you can also bring in other variables which can affect pH. Our tank is not a lab. There are many other forces at play. Source water dKH can change over time, even seasonally in many places. Some municipalities inject things like Sodium Hydroxide to alter pH. And the list goes on. Even a difference in plant mass and CO2 uptake can throw things off.

So then the question is why does it matter? In my experience optimizing CO2 makes every single other thing easier. If you get CO2 right, you have much more leeway as to nutrient dosing, as a wider range will still produce very good results. Folks love to discuss dosing down to the smallest detail. This ratio vs that ratio. Lean vs rich. K must be below NO3. PO4 must be limited. And the list goes on and on. In my experience if you take the time to get CO2 right, these topics become far less important.

So if we can’t trust the CO2 ppm calculation, how do we dial in CO2? First is having a reliably constant flow rate of CO2. Many cheap needle valves drift. Counting bubbles accurately is all but impossible and bubbles are not a uniform measurement. I use a flow meter and even that can have limitations. So the odds of someone’s CO2 ppm being constant is low.

For me the best method is trial and error and patience. Closely observe both fish and plants while dialing in CO2 slowly over a period of time. Plants will provide subtle clues as you get closer to your optimum concentration. If fish show distress time to back it off just slightly. And one thing many don’t consider is that O2 and CO2 are not mutually exclusive. That is you can have and want high levels of each. If you have good surface agitation (O2) you can have higher levels of CO2 without affecting livestock.

I can tell you this. If I see something wonky in my tank, the first thing I do is check and double check CO2 levels. If it’s off I could waste a lot time playing whack-a-mole with ferts when the real issue is something completely different.
_


----------



## Zeus.

GreggZ said:


> Folks will often list tank parameters and say their CO2 is at 30 ppm. But is it? Best answer is “maybe”.





GreggZ said:


> Let’s start with measuring dKH.


Never measure dKH myself or dGH


GreggZ said:


> If I see something wonky in my tank, the first thing I do is check and double check CO2 levels





GreggZ said:


> it’s even true when using calibrated probes.


Correct, only ever calibrated semi regular when using pH probe and I never trust the pH reading unless its the same as a pH buffer a can cross reference.


GreggZ said:


> So then the question is why does it matter? In my experience optimizing CO2 makes every single other thing easier. If you get CO2 right, you have much more leeway as to nutrient dosing, as a wider range will still produce very good results. Folks love to discuss dosing down to the smallest detail. This ratio vs that ratio. Lean vs rich. K must be below NO3. PO4 must be limited. And the list goes on and on. In my experience if you take the time to get CO2 right, these topics become far less important.





GreggZ said:


> First is having a reliably constant flow rate of CO2. Many cheap needle valves drift. Counting bubbles accurately is all but impossible and bubbles are not a uniform measurement.



.


JoshP12 said:


> 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).
> 
> 
> 
> 
> 
> 
> Rubisco concentration light dependent?
> 
> 
> Hi all,  So, I've been thinking :oops:. I recall reading that the argument for stable CO2 during photoperiod was because of the Rubisco concentration in a plant. In other words, getting a stable CO2 is the key to match your light.  If light drives CO2 uptake, and stability of CO2 is needed for...
> 
> 
> 
> www.ukaps.org



Will read the links and digest it ASAP - just got back from holiday and very busy


----------



## Hanuman

MarcusA said:


> @Hanuman , what do you think of this idea: using a basic NDIR CO2 monitor to check CO2 levels in water by placing the monitor in a closed container with some outdoor air and some tank water at the bottom and allowing an equilibrium to become established between the air and water ala Henry's Law. Sort of like a giant drop checker.


I believe I don't have much to add after what was said in above few posts. 😬


----------



## Cavalier_Steve

@Zeus. and @Tim Harrison thank you both for putting an easy to understand thread about CO2 injection, I first started properly dosing CO2 early this year and have learned a lot from various threads, I never really fully understood carrying out a pH profile, now thanks to this post I do and can probably fine tune it a little more accurately, I think I’ve been very lucky with my setup as the Algae is very minimal.
So thanks again both for sharing your information in an easy to understand format, I know this will help so many people that are thinking or joining in there CO2 adventures.

All the best. 
Steve.


----------



## Cavalier_Steve

Sdogg said:


> I have the UP PH controller
> 
> 
> 
> 
> 
> 
> 
> 
> WEIPRO pH CO2 Controller for Planted Aquariums
> 
> 
> Using the pH Controller you can put your CO2 deployment on auto-pilot, and only dose CO2 into your aquarium as and when it's needed.
> 
> 
> 
> 
> www.co2supermarket.co.uk
> 
> 
> 
> 
> 
> 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 said:


> 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.


Your posts regarding this pH controller has intrigued me,  just a quick question though do you have a timer plugged into the controller so that it doesn’t dose overnight or do you simply leave it up to the controller? 
I like the idea of having an extra level of safety margin towards my livestock.
Thank you in advance. 
Steve.


----------



## Sdogg

Cavalier_Steve said:


> just a quick question though do you have a timer plugged into the controller so that it doesn’t dose overnight


Yep, exactly that. The controller is always sensing and trying to control the Co2, but the timer will only allow it during your injection period.


----------



## Yugang

Cavalier_Steve said:


> do you have a timer plugged into the controller so that it doesn’t dose overnight or do you simply leave it up to the controller?


Indeed, I put my controller on a timer.

As the ramp up will be faster than with traditional setup, and stability reached earlier, start less than one hour before lights on and stop one hour before lights off. Just try it out, and make sure that the 0.1 pH stability is reached before photoperiod.

It is the first few hours of photoperiod that are most important, so believe I can accept some pH drift in the last hour or so (I may be wrong on this one).
With low O2 (which could happen during night), lifestock is more sensitive to CO2. Therefore no CO2 injection during the night -- saving CO2 and more comfortable/safe for lifestock.

Hope this helps


----------



## Cavalier_Steve

Sdogg said:


> Yep, exactly that. The controller is always sensing and trying to control the Co2, but the timer will only allow it during your injection period.





Yugang said:


> Indeed, I put my controller on a timer.
> 
> As the ramp up will be faster than with traditional setup, and stability reached earlier, start less than one hour before lights on and stop one hour before lights off. Just try it out, and make sure that the 0.1 pH stability is reached before photoperiod.
> 
> It is the first few hours of photoperiod that are most important, so believe I can accept some pH drift in the last hour or so (I may be wrong on this one).
> With low O2 (which could happen during night), lifestock is more sensitive to CO2. Therefore no CO2 injection during the night -- saving CO2 and more comfortable/safe for lifestock.
> 
> Hope this helps


Thank you both  kindly for answering my questions so quickly, I’m really keen on trying this setup myself.
Yes I wasn’t sure if the pH controller would loose its calibration over multiple power cycles over a month or something weird like that.
Thanks again for your help!
Edit: Sorry for high jacking this thread 🤦‍♂️🙂
Kind regards,
Steve.


----------



## Sacul

Thank you for this write up. After searching for weeks for info, this is the best write up I've seen and very helpful. I just need a bit of clarification. After alot of adjusting CO2 and testing pH I think I'm kind of stable.
Tank water sat 24h in a glass pH 8.23
Tank Kh 8
I can get a drop to 7.2 and keep it stable within 0.1 for the rest of the lights on duration. According to the pH drop of 1 that should be around 30ppm ish. According to the charts it's alot less. Should I just ignore the chart and stick with what I've got? I can't seem to drop any lower, if I turn the CO2 up any more it just keeps dropping the pH until CO2 off and I can't stabilize it. 
Thanks @Zeus. for all your help


----------



## Zeus.

Sacul said:


> According to the charts it's alot less. Should I just ignore the chart


Yes, the chart is a complete waste of time.


----------



## Sacul

Zeus. said:


> *Time it takes to get your target CO2 level*
> The time it takes to reach a CO2 concentration of 30ppm varies with tank size and injection method. About 2hrs is normal for a 50 litre tank, but bigger tanks can take 4 to 5 hours plus.


Hi 
I'm reading through your post again to make sure I've not missed anything. When your talking about the time it takes to reach 30ppm, are you talking about 2hrs of CO2 being injected before the lights come on? Assuming that's what you mean, having a bigger tank I could push the time back at which the CO2 turns on to try and get better saturation by the time lights are on.


----------



## KirstyF

Sacul said:


> Hi
> I'm reading through your post again to make sure I've not missed anything. When your talking about the time it takes to reach 30ppm, are you talking about 2hrs of CO2 being injected before the lights come on? Assuming that's what you mean, having a bigger tank I could push the time back at which the CO2 turns on to try and get better saturation by the time lights are on.



Hi There. Yep that’s what is being said.

However long it takes to get to your 1ph drop is just however long it takes and you ideally want to already be there when the lights come on. 

I’ve a very big tank and it takes 3.5hrs before lights on, with  2 reactors, to hit that 1ph drop. 

If you’re getting a pretty stable level through your photo period but not quite getting to a 1ph drop by the time the lights come on then you can likely leave everything as it is but just turn the Co2 on a bit earlier. 

There is a solid argument to say that it takes a wee while for the plants to get going so if it’s not spot on 1ph the very moment you have lights, it’s not the end of the world, but it’s a good target to have and will make sure that the Co2 is fully available as soon as the plants need it. 😊


----------



## Sacul

KirstyF said:


> If you’re getting a pretty stable level through your photo period but not quite getting to a 1ph drop by the time the lights come on then you can likely leave everything as it is but just turn the Co2 on a bit earlier.


I thought I was getting pretty stable level but I've noticed it is still dropping towards the evening. My thinking was if I turn it on even earlier, was 3hrs now testing 4hrs to see if I can get it to drop even lower before lights on then hopefully it will stable out a bit more during the photo period


----------



## Hufsa

Sacul said:


> I thought I was getting pretty stable level but I've noticed it is still dropping towards the evening. My thinking was if I turn it on even earlier, was 3hrs now testing 4hrs to see if I can get it to drop even lower before lights on then hopefully it will stable out a bit more during the photo period


My understanding is that injection rate controls how fast your drop is, but surface agitation / off-gassing controls how steady the level is and effectively stops the CO2 concentration from getting higher than you want. 
The final range you end up in is a result of both factors.

Therefore if you want a steadier level during lights on, I would look at your surface agitation. Then after that adjust injection as needed.


----------



## KirstyF

Sacul said:


> I thought I was getting pretty stable level but I've noticed it is still dropping towards the evening. My thinking was if I turn it on even earlier, was 3hrs now testing 4hrs to see if I can get it to drop even lower before lights on then hopefully it will stable out a bit more during the photo period



What is your surface agitation like? Whilst it may seem counterintuitive, a good level of surface movement IMO helps to stabilise things too. 😂 Lol. Last message just popped up so……what @Hufsa just said. 👍

I would therefore make sure you are getting a good surface ripple, do a profile again and then start a bit earlier if you need to.


----------



## Sacul

Hufsa said:


> Therefore if you want a steadier level during lights on, I would look at your surface agitation


This is what I though aswel from what I have read, I have a 3200lh powerhead pointed at the surface of the tank aswel as a 1450lh filter pointed at the surface plus a skimmer so would say I have pretty good surface agitation. It is a 5ft tank so more agitation on one side than the other but still movement across the whole surface.


----------



## Zeus.

Sacul said:


> Hi
> I'm reading through your post again to make sure I've not missed anything. When your talking about the time it takes to reach 30ppm, are you talking about 2hrs of CO2 being injected before the lights come on? Assuming that's what you mean, having a bigger tank I could push the time back at which the CO2 turns on to try and get better saturation by the time lights are on.


Yes


Sacul said:


> a bigger tank I could push the time back at which the CO2 turns on to try and get better saturation by the time lights are on.


A bigger tank may take longer and a small tank less time.


Sacul said:


> I thought I was getting pretty stable level but I've noticed it is still dropping towards the evening. My thinking was if I turn it on even earlier,





Hufsa said:


> My understanding is that injection rate controls how fast your drop is, but surface agitation / off-gassing controls how steady the level is and effectively stops the CO2 concentration from getting higher than you want.
> The final range you end up in is a result of both factors.
> 
> Therefore if you want a steadier level during lights on, I would look at your surface agitation. Then after that adjust injection as needed.


@Hufsa nails it, it is a blend of the injection rate and the surface agitation. With higher surface agitation you will need a higher injection rate to compensate for the increase loss of CO2 from the surface, But the pH drop will be quicker and more stable.


----------



## Sacul

Zeus. said:


> With higher surface agitation you will need a higher injection rate to compensate for the increase loss of CO2 from the surface, But the pH drop will be quicker and more stable.


So possibly my injection rate is too high if the pH keeps dropping. My thinking was, I think I have enough surface agitation but because the pH keeps dropping, if I push the CO2 on time back an hour it could drop that little bit more before the photo period. As long as the livestock is still safe then hopefully stable out a bit more during the photo period.


----------



## KirstyF

Can you post your full profile results from gas on to lights off? Might help folks to give some advice specific to your situation. 😊


----------



## Yugang

Zeus. said:


> To find a tank’s CO2 level or baseline before injection starts, take a clean glass of tank water and leave it at room temp for 24 hrs after which take a pH reading. This will be the baseline or degassed pH of your tank water.


@Zeus.  , although above is perfectly valid, I have another suggestion for an edit that may make life for the CO2 beginner a little easier.

Rather than having your aquarium water outgas for 24 hours, you may fill a jar with 10% aquarium water. Go outdoor, where ambient CO2 is predictable, open the jar lid and let fresh air in. Then shake violently, for the water to degas into the trapped fresh air in the jar. Open lid another 2-3 times, each time shake, and we're all set. I have my degassed reading within a minute, rather than 24 hours.


----------



## Hanuman

Yugang said:


> @Zeus. , although above is perfectly valid, I have another suggestion for an edit that may make life for the CO2 beginner a little easier.
> 
> Rather than having your aquarium water outgas for 24 hours, you may fill a jar with 10% aquarium water. Go outdoor, where ambient CO2 is predictable, open the jar lid and let fresh air in. Then shake violently, for the water to degas into the trapped fresh air in the jar. Open lid another 2-3 times, each time shake, and we're all set. I have my degassed reading within a minute, rather than 24 hours.
> 
> View attachment 189095



I am not convinced you can fully degass water that fast and bring it to equilibrium with a few shakes, but since I am no one I’ll let the pro scientist confirm this.


Sent from my iPhone using Tapatalk


----------



## Yugang

Hanuman said:


> I am not convinced you can fully degass water that fast and bring it to equilibrium with a few shakes, but since I am no one I’ll let the pro scientist confirm this.
> 
> 
> Sent from my iPhone using Tapatalk


You have a point, perhaps for some it takes one or two minutes more  
Easy to verify making multiple measurements and see of pH rises further with more shaking. 



Yugang said:


> shake violently


That's what I mean, assuming a more experienced UKAPS CO2 degasser.


----------



## Sacul

Thanks again guys, I'll do another degas and pH profile. I know what my previous degas values were so I'll try the shake method aswel and see if I can get the same results. Like you say I can always shake it a few more times for verification


----------



## JacksonL

Yugang said:


> @Zeus.  , although above is perfectly valid, I have another suggestion for an edit that may make life for the CO2 beginner a little easier.
> 
> Rather than having your aquarium water outgas for 24 hours, you may fill a jar with 10% aquarium water. Go outdoor, where ambient CO2 is predictable, open the jar lid and let fresh air in. Then shake violently, for the water to degas into the trapped fresh air in the jar. Open lid another 2-3 times, each time shake, and we're all set. I have my degassed reading within a minute, rather than 24 hours.
> 
> View attachment 189095


I have been experimenting with this, I have found 3.5 minutes of shaking is what it takes to get my water to read the same pH as a 60 hour degas (which is what I have found it takes my water to fully degas)


----------



## Zeus.

Yugang said:


> @Zeus.  , although above is perfectly valid, I have another suggestion for an edit that may make life for the CO2 beginner a little easier.
> 
> Rather than having your aquarium water outgas for 24 hours, you may fill a jar with 10% aquarium water. Go outdoor, where ambient CO2 is predictable, open the jar lid and let fresh air in. Then shake violently, for the water to degas into the trapped fresh air in the jar. Open lid another 2-3 times, each time shake, and we're all set. I have my degassed reading within a minute, rather than 24 hours.
> 
> View attachment 189095



@X3NiTH ( aka ' The Half Blooded Prince) did a great post on it, I didn't add details about it as I was trying to get it as brief as possible. When I get time (or if someone provides a link to his thread/post) I will add a link to bottom of post. His post is more valid as he is our resident chemist after all


----------



## Yugang

Zeus. said:


> @X3NiTH ( aka ' The Half Blooded Prince) did a great post on it, I didn't add details about it as I was trying to get it as brief as possible. When I get time (or if someone provides a link to his thread/post) I will add a link to bottom of post. His post is more valid as he is our resident chemist after all



I believe I found the post you mention, maybe there are more detailed posts from @X3NiTH but couldn't find


X3NiTH said:


> There’s a quicker way to do this and that’s to draw the sample and put it in a lidded container and shake the bejeezus out of it for a couple minutes or so and periodically exposing the sample to ambient air, you can then test the pH with a pH Pen or a dip strip.





JacksonL said:


> I have been experimenting with this, I have found 3.5 minutes of shaking is what it takes to get my water to read the same pH as a 60 hour degas (which is what I have found it takes my water to fully degas)


This is a good start thank you @JacksonL 
Of course details matter for having the maximum efficiency - just a little water in the jar not too much, open lid in fresh air regularly, and shake the hell out of it.
I shake out 0.5-1 pH in a minute, and of course the efficiency decreases as the water gets closer to the full ambient equilibrium state. By taking multiple measurements between shakes, one gets a good feeling if any more shaking is further increasing the pH or not.

Perhaps I may go a little off topic here, sharing some of my gut feel / intuition  about CO2 gas exchange. One of my favorite professors, many years ago, taught me to always try and do estimations for having a feel for a complex system, before doing complex computation, as it is better to be approximately right than to be precisely wrong. So the below is nothing scientific, but at least for me helpful to understand what I am trying to do.

In steady state, my reactor injects about 5 bubbles per second. I took pictures of the reactor, and I count approximately 50 bubbles chaotically moving around in flow.  Bubbles are typically 3-5 mm diameter, both injected as well as in the pupulation of 50.
As we have steady state, injecting 5 bubbles per second, we may assume also 5 bubbles disappear per second. If 5 bubbles disappear from a population of 50, this means that the average lifetime of a 3-5 mm diameter bubble is as short as 10 seconds ...
This estimation ignores a lot of  physics and statistics going on in the reactor, is not accurate and not scientific at all. My key takeaway is that gas exchange of pure CO2 to pure water is remarkably fast.

I am also experimenting with my CO2 Spray Bar . This is a half pipe with 1 inch diameter, where gas can exchange at the open interface between CO2 and aquarium water. I have not yet done precise measurement, but when I turn off CO2 injection I see the half pipe already 50% empty in about 15 minutes. Again, how remarkably fast is CO2 exchange with water.

So why does it take 24 hours, or even longer to degas aquarium water in a jar standing outside? When above two examples show how fast gas exchange can be? This is probably related to transport phenomena in the steady water in the jar, absence of flow and turbulence. I am just guessing here. But I am not surprised that violently shaking up the jar, each time in fresh air, does speed up the process a lot.


----------



## Hanuman

Well I learnt something today. Let's shake it from now on.


There were other "Shake it" videos out there some of which were far from appropriate for this forum. I'll let you Youtube it and you'll understand. (Hint: Bella Thorne).


----------



## Yugang

Hanuman said:


> Well I learnt something today. Let's shake it from now on.
> 
> 
> There were other "Shake it" videos out there some of which we far from appropriate for this forum. I'll let you Youtube it and you'll understand.



I would suggest @Hanuman to post this under What other hobby's do you have? 
​


----------



## JacksonL

Yugang said:


> I believe I found the post you mention, maybe there are more detailed posts from @X3NiTH but couldn't find
> 
> 
> 
> This is a good start thank you @JacksonL
> Of course details matter for having the maximum efficiency - just a little water in the jar not too much, open lid in fresh air regularly, and shake the hell out of it.
> I shake out 0.5-1 pH in a minute, and of course the efficiency decreases as the water gets closer to the full ambient equilibrium state. By taking multiple measurements between shakes, one gets a good feeling if any more shaking is further increasing the pH or not.
> 
> Perhaps I may go a little off topic here, sharing some of my gut feel / intuition  about CO2 gas exchange. One of my favorite professors, many years ago, taught me to always try and do estimations for having a feel for a complex system, before doing complex computation, as it is better to be approximately right than to be precisely wrong. So the below is nothing scientific, but at least for me helpful to understand what I am trying to do.
> 
> In steady state, my reactor injects about 5 bubbles per second. I took pictures of the reactor, and I count approximately 50 bubbles chaotically moving around in flow.  Bubbles are typically 3-5 mm diameter, both injected as well as in the pupulation of 50.
> As we have steady state, injecting 5 bubbles per second, we may assume also 5 bubbles disappear per second. If 5 bubbles disappear from a population of 50, this means that the average lifetime of a 3-5 mm diameter bubble is as short as 10 seconds ...
> This estimation ignores a lot of  physics and statistics going on in the reactor, is not accurate and not scientific at all. My key takeaway is that gas exchange of pure CO2 to pure water is remarkably fast.
> 
> I am also experimenting with my CO2 Spray Bar . This is a half pipe with 1 inch diameter, where gas can exchange at the open interface between CO2 and aquarium water. I have not yet done precise measurement, but when I turn off CO2 injection I see the half pipe already 50% empty in about 15 minutes. Again, how remarkably fast is CO2 exchange with water.
> 
> So why does it take 24 hours, or even longer to degas aquarium water in a jar standing outside? When above two examples show how fast gas exchange can be? This is probably related to transport phenomena in the steady water in the jar, absence of flow and turbulence. I am just guessing here. But I am not surprised that violently shaking up the jar, each time in fresh air, does speed up the process a lot.


As far as details go, I use one of the small test vials that come with Salifert NO3 tests. Half fill it, lid on and shake for a minute, then open it up for a few seconds, then repeat, then repeat again except the last shake goes for 1.5 minutes. I then leave it open for a bit to settle, no defined time, I generally do whatever needs doing on the tank, cut off older leaves, trim plants, check equipment etc.
I had been trialling it with 1 minute/2minute/3minute and 4 minute shaken containers, testing them, then at the same time taking a sample and letting it sit for 3 days. 3.5 minutes seems the sweet spot for my tank, but I assume there may be differences between tanks depending on water chemistry.


----------



## Yugang

This is what I use. Only fill for 10% or so, go outside and go crazy for a few minutes.


----------



## Sacul

KirstyF said:


> Can you post your full profile results from gas on to lights off? Might help folks to give some advice specific to your situation. 😊


After doing a new pH profile yesterday my drop seems to have gone back to stable. Not sure what happened on that odd day where it was out with the last reading being 7.16. I did the degas jar shake which made my degassed pH value higher than my 24hr sat glass of water.
24hr glass 8.23
Jar shake 8.32
At lights on I was at 7.34 and lights off 7.29.
Although it seems like I'm getting the 1ph drop, my drop checker still isn't lime green. It's still more of a darker green. Is this a problem or not really?


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## Hanuman

Yugang said:


> I would suggest @Hanuman to post this under What other hobby's do you have?


Not a fan of K pop.😎 - I much prefer classical music.


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## Hanuman

@Yugang This shaking thing was discussed here too by CEG4048.








						Spray Bar and CO2 Diffuser placement confusion
					

I think I have a decent flow as I can see that the leaves are gently swaying. The spray bar runs accross the tank and has 6 holes roughly 1/8" diameter. Is there a way to test if the flow is a complete circular motion by adding something to the tank?  Hi Monis,               Yes, you can cut a...



					www.ukaps.org


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## Yugang

Hanuman said:


> @Yugang This shaking thing was discussed here too by CEG4048.
> 
> 
> 
> 
> 
> 
> 
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> Spray Bar and CO2 Diffuser placement confusion
> 
> 
> I think I have a decent flow as I can see that the leaves are gently swaying. The spray bar runs accross the tank and has 6 holes roughly 1/8" diameter. Is there a way to test if the flow is a complete circular motion by adding something to the tank?  Hi Monis,               Yes, you can cut a...
> 
> 
> 
> www.ukaps.org


It is a very logical method to speed up outgassing, but @ceg4048 being a resident of Chicago I had expected a more localised approach at 300 rpm


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