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Discussion Starter #1
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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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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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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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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Discussion Starter #7 (Edited)
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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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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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...

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

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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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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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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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Discussion Starter #16 (Edited)
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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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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