Dialling in the CO2 injection Rate and CO2 Profiles

[Sdogg]

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

UP pH CO2 Controller for Planted Aquariums

Using the UP pH Controller you can put your CO2 deployment on auto-pilot, and only dose CO2 into your aquarium as and when it's needed. It can also act as a fail-safe against 'end of tank dump' or accidental over-dosing.

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.

 

[foxfish]

I have the UP PH controller

UP pH CO2 Controller for Planted Aquariums

Using the UP pH Controller you can put your CO2 deployment on auto-pilot, and only dose CO2 into your aquarium as and when it's needed. It can also act as a fail-safe against 'end of tank dump' or accidental over-dosing.

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?

 

[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).

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

 

[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?

 

[JoshP12]

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]

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]

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.

 

[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

 

[Hanuman]

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]

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]

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]

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]

@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.]

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

Let’s start with measuring dKH.

Never measure dKH myself or dGH

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

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.

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.

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.

.

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]

@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 @Guest 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]

I have the UP PH controller

UP pH CO2 Controller for Planted Aquariums

Using the UP pH Controller you can put your CO2 deployment on auto-pilot, and only dose CO2 into your aquarium as and when it's needed. It can also act as a fail-safe against 'end of tank dump' or accidental over-dosing.

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.

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.
[/QUOTE]
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]

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.