# CO2 consumption survey



## BluesBoy (Jul 2, 2004)

For the latest couple of months I have done some automatic pH-measurements in my tank. I use an own built pH-controller/meter. It has a serial PC-interface which I can use to see how the CO2 is changes due to different conditions/parameters 24 h/day. It is a great tool to gain knowledge of the CO2 level in planted tanks. Of course, it can run as an ordinary controller as well. The housing is a $5 modified timer and the PCB is home built with a $2 micro controller as the hart of the system:
http://193.12.137.241/bluesboy/viewimage.php?id=205
http://193.12.137.241/bluesboy/viewimage.php?id=209

The pH-value and the status of the solenoid valve is stored on my web sever at regular basis 24h per day with a client-server solution. This is how the result could look like if I select one day:
http://193.12.137.241/bluesboy/pHplott.php?t=2004-12-25

The black line is pH-level and the red is the solenoid valve (on=7, off=6).

Recently I found out how much the (surface) water circulation is affecting the CO2-level:
http://193.12.137.241/bluesboy/aquabase/plottlinks/sum.php

To put some more data to this subject in general, I have just started a very simple survey to see how much CO2 different tanks are consuming. It is quite rough, but it's interesting to see how it can differ. The main input is how long time a known mount of CO2 is lasting (NOT DIY). To be able to compare different set-ups, I have added some extra information as well.

I would be very happy if you could add your parameters in my database to get it more complete. Some Swedish forum members have just started.

http://193.12.137.241/bluesboy/aquabase/consumption/sum.php

Just follow the link "Add new period". Any questions? Just post it here or send me an email.

Thank you in advance.


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## defdac (May 10, 2004)

Interesting. I'm in!

Why is there no response in this interesting thread?


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## gnatster (Mar 6, 2004)

Interesting thread. I added my info

Just for clarification a US 5lb bottle is 2270g?

My CO2 use seems to be on the low end, I find that surprising being the tank is open, the circulation is heavy and I keep the level above 40ppm.


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## Sir_BlackhOle (Jan 25, 2004)

If I had anything other than DIY I would love to participate! Someday soon i hope!


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## gpodio (Feb 4, 2004)

This sounds like an interesting idea, perhaps the end of the "24/7 or not" debates 

I did similar observations on my own tanks but it will be nice to see the results of a larger number of tanks with varying conditions.

Giancarlo


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## JanS (Apr 14, 2004)

Oh darn, I just realized I put down a 10# tank.... No wonder the consumption is so high.... #-o 
It it editable or do I have to start over?


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## BluesBoy (Jul 2, 2004)

Nice to get more data to play with :smile: 
It will be interesting to see the variations between tanks and then start to find out parameters affecting the consumtion.



> It it editable or do I have to start over?


No, just send me an e-mail [email protected] with new data and I will correct it.
However, if you have more than one CO2-period - just add it to the list with the same name.


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## Laith (Sep 4, 2004)

Very interesting...

I seem to be using abnormally small amounts of CO2 even though the ph/KH is giving me in general over 30mg/l...

But I'm not getting heavy pearling; some, but not alot. Tom Barr has been repeating over and over again that most people's CO2 levels are probably lower than they think.

Maybe this is my case?


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## BluesBoy (Jul 2, 2004)

I have now changed the data for JanS (bottle size). The new consumption is 7.13.


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## JanS (Apr 14, 2004)

Thank you BluesBoy.  That sounds much better.....


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## BluesBoy (Jul 2, 2004)

Hi again!
Anyone who has a new CO2 period to add to my database? 
Interesting to see that some of us have reduced the consumption quite well after reduction of the surface circulation and/or using a controller.

http://193.12.137.241/bluesboy/aquabase/consumption/sum.php

Please, don't hesitate to add a period here :
http://193.12.137.241/bluesboy/aquabase/consumption/add.php


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## shalu (Oct 1, 2004)

Laith said:


> Very interesting...
> 
> I seem to be using abnormally small amounts of CO2 even though the ph/KH is giving me in general over 30mg/l...
> 
> ...


You entered "500" grams co2 in the table. Only a 1.1 lb CO2 tank?


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## Laith (Sep 4, 2004)

Yes, that was before I switched to a 2.3kg (5lb) refillable tank about 2 months ago.

Over here you can buy CO2 kits that come with a special regulator for use with small 500g disposable tanks. Now I'll just use the disposable tank when I go to exchange my refillable tanks.


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## plantbrain (Jan 23, 2004)

defdac said:


> Interesting. I'm in!
> 
> Why is there no response in this interesting thread?


Few folks have access to pH data logging(I have them).

They are quite useful and given the importance of CO2, not a bad idea to check out.

But..................

Basing the solely on pH does not tell everything, you need to measure and check the KH as well carefully and often to determine the CO2 as well.

Hopefully it does not change, but do not assume it does not.................
KH will burn you and has burned anyone that's used CO2 for awhile whether they realized it or not.

I do not see any water change pH changes in your data. We should see a spike after a water change. I data log dissolved O2, Temp, as well as pH and conductivity.

There are a few companies that make such devices, Neptune controllers have a few functions like pH/Temp etc, they don't have Dissolved O2 though, YSI does though(these are about 2500$), the Neptune's are about 400-600$.

==========

Laith, just add more and see.

Regards, 
Tom Barr


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## plantbrain (Jan 23, 2004)

Ah there's a WATER change pH spike in the last link! 

While your pH measurements might be accurate, many folks are not. KH measurements are also different, often with an error of 10ppm or more.
pH and other buffers from tannins, organic loading from plant decay/fish waste etc also add CO2 sources as do the critter/fish loads.

pH measurement also can vary a great deal due to the light ballast and other electrical equipment.

You will want to look at trends over a month's time also. 

Regards, 
Tom Barr


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## BluesBoy (Jul 2, 2004)

plantbrain said:


> While your pH measurements might be accurate, many folks are not. KH measurements are also different, often with an error of 10ppm or more.
> 
> Regards,
> Tom Barr


Yes, I agree. However, as I mentioned in the first post the aim of this simple survey is to see how much CO2 different tanks are consuming in a long term with different set-ups. Not to measure accurate pH(CO2)-levels. 
The pH-logging is just a great tool to se how the tank is responding on different changes in the set-up. The CO2 consumption database is the long-term feedback. For instance: I have reduced my CO2 consumption about 50% (it lasting double mount of time) just to change the cirkulation in the tank


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## plantbrain (Jan 23, 2004)

BluesBoy said:


> Yes, I agree. However, as I mentioned in the first post the aim of this simple survey is to see how much CO2 different tanks are consuming in a long term with different set-ups. Not to measure accurate pH(CO2)-levels.
> The pH-logging is just a great tool to se how the tank is responding on different changes in the set-up. The CO2 consumption database is the long-term feedback. For instance: I have reduced my CO2 consumption about 50% (it lasting double mount of time) just to change the cirkulation in the tank


Oh heck, I'm not suggesting there's too much error, but just be aware of it.

There are two seperate main things influncing CO2: plant uptake/consumption and off gassing.

There are other things such as CO2 limitations that can force bicarbonate uptake of HCO3- , which changes the CO2 level that's based on the pH, amount organic matter/bacterial respiration, fish load etc

Consumption of CO2 is based on many factors, I've done a fair amount with terrestial systems and LiCor instruments to this extent. This deals with plant CO2 consumption and not off gassing.

Lighting units need to be the same to have a fair comparison, now we get into measuring light which is perhaps even worse. More PAR light=> more CO2 consumption demand. PAR meters are not cheap and many assume they can use lux, you can't do that.

I can have high high PAR and low lux, I can have high Lux and low PAR.
Lux is measured based on our eye, 555nm. PAR is 400-700nm and we could very little Green and lots of Red/Blue in our bulbs. That is huge unknown between tanks compared here and or anywhere.

I'm unwilling to make the assumption lux is a good unit for light.

More CO2=> more nutrient demand and so on. 
If one is lacking then the CO2 consumption rate will decline, as will the O2 level, which is a better paratmeter in terms of plant growth/health, tank health.

I think labeling with 14CO2 would be the best way to see. 
Not a hobby based thing.
I need to think about it some, I'll see if I can come up with a better method to measure CO2 use in aquatic systems for plants.

But I believe the utility for this data logging is better trend analysis, better methods to reduce CO2 loss and methods to measure such losses or changes that affect CO2 levels.
It makes a good ruler there and I think more folks should do this and the set up is fairly cheap DIY. Thanks, that will be useful for hobbyist rather than the costly stuff I have.

You may want to consider O2 meters and data logging, combined with CO2, this is a very useful tool for CO2 use/plant production.
I have both, as well as temp, Conductivity and Redox.

I think pH/O2 are the two main probes worth using. 
While data logging is nice, you can still hand write the data off a pH meter and graph it like like this in Excel etc.

Let me think about some possible ways to improve this measurement of plant consumption and tank consumption to get more standard results that cover the bases better.

Good topic and focus. Folks often return to the basics to realize they are more complex than they once thought.

Regards, 
Tom Barr

www.BarrReport.com


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## pacolopezmujica (Jun 19, 2005)

*CO2 measurments*

Is the TETRA CO2 tester reliable?
Thanks,
Paco


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## czado (May 26, 2005)

BluesBoy,

Do you have a schematic and parts list (or link) for your serial interface board? Great project!


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## Laith (Sep 4, 2004)

pacolopezmujica said:


> Is the TETRA CO2 tester reliable?
> Thanks,
> Paco


The easiest way to determine CO2 levels is to measure your KH (in degrees) and pH and then use a CO2 table. The table correlates the relationship between KH and pH and gives you the CO2 concentration.

Here is a good link for the table and more info:

http://www.csd.net/~cgadd/aqua/art_plant_co2chart.htm


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## Happy Camper (Jul 22, 2004)

Laith said:


> The easiest way to determine CO2 levels is to measure your KH (in degrees) and pH and then use a CO2 table. The table correlates the relationship between KH and pH and gives you the CO2 concentration.
> 
> Here is a good link for the table and more info:
> 
> http://www.csd.net/~cgadd/aqua/art_plant_co2chart.htm


I agree with Laith, whats the point in doing all this data mining? Why make mountains out of molehills? Just add more co2, check your charts and be done with it. Keep it simple 

Kind regards
Cameron


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## BluesBoy (Jul 2, 2004)

czado said:


> BluesBoy,
> 
> Do you have a schematic and parts list (or link) for your serial interface board? Great project!


I'm just upgrading my controller/logger for more features. When it's done I'll put all schematics and BOM lists on my blog.



Happy Camper said:


> I agree with Laith, whats the point in doing all this data mining? Why make mountains out of molehills? Just add more co2, check your charts and be done with it. Keep it simple


Yes it's a great method if you don't want to learn more


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## plantbrain (Jan 23, 2004)

But........what are you really learning?
Is this really going to teach you something and answer your original question?

There is a huge number of factors influencing the CO2 offgassing, this changes day to day, hour to hour, month to month, temp to temp, aquarist to aquarist, tank to tank, plant species to plant species, critter and bacteria contribution to CO2 etc.

I think you will have a lot of trouble correlating useful data from this.
Isolating things down and then building from there is a more useful approach and folks can do this relatively easily.

"Learning" can learning from your mistakes and past assumptions.
It's good to learn from experience, as long as it's not your own.

Testing and all is fine, but do not assume it's "learning" something useful.
You need to be more focused in your question and set up to get a good idea without a massive amount of error and confounding problems.

I focus on what I can prove or at least get a good idea on.
Bubble rates are often used elsewhere and give a rougher estimate of CO2 use.

I think given the variability in tanks, time of measurement, plant types etc, that's "rough" enough and about as close as you are going to get to draw anything useful from.

Check around for bubble rates.

But.......I like to see the graphs with the water changes, and DO measurements added, these things will tell you something and help you learn more.

All is not lost certainly.
Mistakes are how we learn also.
You can learn the hard way(been there done that).

Lord knows I make many, that way I know what screwed up and allows me to help folks solve their issues and know where they might go wrong.
I do not make the same mistakes twice often these days.

There is another level going on here also, some folks like to see what their tank does and play around with CO2 consumption, even if they gain nothing useful in terms of horticulture.

Over time, they will focus more on their CO2 and the measurement.
That is a very good thing.

But the original premise and assumptions do need some work, you can get some useful stuff certainly, but it might not be what you originally intended.

I do a lot of testing, and I have all sorts of gadgets, meters, spectrophotometers and the $ and job to play with them.

I am interested in your original question, but it's difficult to tease aparat all the issues, we'd need to focus on a more isolated system and then apply/extrapolate from there.

Assume a maximum CO2 consumption rate(very high light, fast growers, non limiting nutrients etc). From there everything else is less.
You can run either in blocks or use several tanks that are indentical as you can make them.

Regards, 
Tom Barr


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## BluesBoy (Jul 2, 2004)

plantbrain said:


> But........what are you really learning?


I have learned a lot.

By measure my pH-value 24 hours a day and visually compared the pearling/bubble rate from the plants it helped me so far to:
+ Improve my reactor a lot
+ Optimized the circulation in my tank. (I do not have to re-fill the CO2 bottle so often now)
+ Understand that plants shadowing is a great factor (reduced lights)
+ Understand that my nutrient test kit's is fooling around and telling me that there is enough N, P, K etc. 
+ Simulate a quite good controller (steady pH-level 24 h) by a simple time schedule (timer)
+ Understand how easy it is to be cheated by simple drop-tests and assuming wrong CO2 levels

I'm happy with that. I'm a hobbyist.



plantbrain said:


> Is this really going to teach you something and answer your original question?


Which question?

Again: the survey was only meant to be a rough comparison between different set-up's. I thought it would be interesting to see if the consumption was in the same *range* with similar set-up's. If the consumption is reduced 50 % with the same pearling/bubble rate from the plants - I'm happy with that as well.

For the moment I'm playing around with different water circulation speeds, parallel with studies of data simulation models to get a better understanding of the Prandl's layer but I think I have to stop there. To many parameters involved which I can't measure/check 100% with my simple equipment makes it impossible to get correct result out from it.


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## plantbrain (Jan 23, 2004)

BluesBoy said:


> I have learned a lot.
> 
> By measure my pH-value 24 hours a day and visually compared the pearling/bubble rate from the plants it helped me so far to:
> + Improve my reactor a lot
> ...


These are all good things as far as optimizing the CO2 levels.
I'm not sure you are getting an "uptake rate" here by plants.
Learning to use CO2 better is a good goal. But is the rate what you are learning and comparing here? You are reducing losses it seems like to me. 
That is a great goal, no issue about that.

Something I nag folks often about.
Going through the process here you have outlined definitely helps that.

Circulation is often discussed, I use spray bars along the bottom of the tank blowing out into the plants horizantal to the substrate. I make certain I have some moderate surface movement.

Yes, poor test kits and measurement are very bad enemies to the planted aquarist. Better measurements and stability over the lighting peroid is the critical thing you will find. Whether it's over 24 hours or over 10, all that is signficant is a good CO2 level over the lighting time.
You can add more CO2 if you add CO2 only during the lighting peroid.

You can try that later if you are interested.



> Again: the survey was only meant to be a rough comparison between different set-up's. I thought it would be interesting to see if the consumption was in the same *range* with similar set-up's. If the consumption is reduced 50 % with the same pearling/bubble rate from the plants - I'm happy with that as well.


Certainly!



> For the moment I'm playing around with different water circulation speeds, parallel with studies of data simulation models to get a better understanding of the Prandl's layer but I think I have to stop there. To many parameters involved which I can't measure/check 100% with my simple equipment makes it impossible to get correct result out from it.


My questions are meant to have you consider the issues, rather than put anyone on the spot, I like what you have done here, it's very very helpful in terms of improving CO2 in people's tanks.

About 90-95% of all algae and plant health issues are CO2 with folks on the forums.

Yes, you get out too far and you cannot assume much by the results.
But a rough estimate is interesting, I've found most of my tanks that do well all have a very low loss ratio.

This also improves the responsiveness to the CO2 system.
More control there is a good thing.

Regards, 
Tom Barr


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## BluesBoy (Jul 2, 2004)

> My questions are meant to have you consider the issues, rather than put anyone on the spot, I like what you have done here, it's very very helpful in terms of improving CO2 in people's tanks.


Thanks! I really appreciate your suggestions and ideas.


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