C02 Charts

Wö£fëñxXx

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Jan 24, 2005
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Tom, You made a post a few days ago and post a link to this C02 chart,
http://www.aquatic-plants.org/articles/khph_table/khph_table.html
I bookmarked it for future reference, as I was looking over some things, I noticed, actually I could not help but notice that it is way off from all the other C02 charts,
TheKrib
http://www.thekrib.com/Plants/CO2/kh-ph-co2-chart.html
Chuck's
http://www.csd.net/~cgadd/aqua/art_plant_co2chart.htm

With all of your studies, have you discovered something else we don't know? :D

Thanks
 

Tom Barr

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Re: C02 Charts

There's some debate about the charts, we use something quite different in the lab. I do suggest using the chart as a guide, but you are not bound to it. Adding more CO2 often does not hurt and solves something issues many folks have.

If you have plenty of light/Nutrients etc, then an excellent experiement is to vary the CO2 and see what is the optimal range.

Bump it up just hair each week, till you hit the fish toxicity range where the fish act all funny.

If you feel confident that the range is 40-50ppm or so, you can back off and not go further.
Adding more is really not needed beyond that but some pH test kits/probes are whacky.

Most test kits measure more CO2 than is actually there.
So you often get false positives.

So even with a perfect chart, it's still only as good as the measurement.

You'll find me less inclined to trust your 5$ test kits and more inclined to trust the plants and algae presence..............

Regards,
Tom Barr
 

Ian H

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Jan 24, 2005
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Re: C02 Charts

I agree with Tom,the charts are only a rough guide.The Aquatic-Plants one has figures that look difficult to achieve realistically. The flora and fauna indications in your tank are the guide.

I managed to completely screw my tank balance by sticking too rigidly to the charts. I found that my Kh test kit was giving a reading that was half of the true one. Since this discovery. and replacing the faulty kit, I have reduced my CO2 input to 1 bubble per 3 seconds against 1 per 1 and the plants are responding with the right results.

Ian
 

m lemay

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Jan 23, 2005
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Re: C02 Charts

This has been my experience. Right now I have a measured/chart co2 level of 50ppm. The plants are doing great and no fish stress. When I had a measured level 30-35 ppm co2 I was having problems with brown algae and slow growth.

My reccomendation , don't be afraid to crank up the co2, watch the fish for signs of stress and the plants for good growth. IME its not so much high CO2 levels that stress the fish but a lack of O2. A small surface current can safeguard the fish at night if your worried. CO2 is relatively cheap.

Marcel
 

Bill

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Re: C02 Charts

I'm sure Tom is right, when I following he advice my tanks always seems to get better.

But the difference in charts is crazy. If you have a pH of 6.6 and a KH of 5 on chart your CO2 is 38 and on the other it is 93. that's is some disagreement.

I have been running my CO2 higher lately watching the plants and the fish with a lot better results, I was trying to stay in the 30 ppm range but I have seen better plant growth watching the plants.

Bill
 

Wö£fëñxXx

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Re: C02 Charts

Bill said:
But the difference in charts is crazy. If you have a pH of 6.6 and a KH of 5 on chart your CO2 is 38 and on the other it is 93. that's is some disagreement.



Bill
That was my point in posting this, that is what threw me for a loop, I know to use these as simple guide's, but when I seen the massive difference between this one and the other's I was like whaaaaa???
 

Steve Hampton

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Re: C02 Charts

Bill said:
I'm sure Tom is right, when I following he advice my tanks always seems to get better.

But the difference in charts is crazy. If you have a pH of 6.6 and a KH of 5 on chart your CO2 is 38 and on the other it is 93. that's is some disagreement.

I have been running my CO2 higher lately watching the plants and the fish with a lot better results, I was trying to stay in the 30 ppm range but I have seen better plant growth watching the plants.

Bill

The problem with the DFW chart is one of formatting. The axis for the pH headings should move to the right two places...meaning that 8.0 should be the furthest to the right and on the left it should begin with 6.0 not 6.4...all the results will mirror the other charts very closely when this formatting error is corrected. Moving the pH number two places to the right will then result in a pH of 6.6 with a KH of 5 being equal to 37 ppm of CO2. Good catch!
 

Tom Barr

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Re: C02 Charts

If some one said a pH/KH of 6.6/5 was 93ppm, I'd say they are wrong as well:)

We have one on the sfbaaps.com site as well,

http://www.sfbaaps.com/reference/table_01.shtml

It's a better one actually.

I don't think in terms of a table any more though, it's gone graphically and into millimoles.

Still....... everyone here has mentioned that trusting the kits when the indicators are still an issue, has learned a valuable lesson.

When helping other folks, approach this issue from the plant and algae perspective, not the test kit parameters and readings. They can help but are not the end all. They can be and often are incorrect.... the algae and the plants never are.


A profound thought to ponder long and hard on.
That principle is still used long before I knew much about plants and science or even much about CO2.

Regards,
Tom Barr
 

AV8TOR

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Jan 23, 2005
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Re: C02 Charts

Silly question, (but I also believe that no question is too silly)
I use a digital pH meter with 0.01 resolution. Is it safe to say you can interpolate between an indicated pH of 7.1 by averaging the difference between 7.0 and 7.2 on these charts?

The math does not seem to work though. If you use the chart with a kH of 3.5 and a pH of 7.0 and 7.4 to find a pH of 7.2
10.3-4.1 = 6.2, 6.2/2= 3.1, 3.1+4.1=7.2 yet the pH for 7.2 is 6.5.

This is from Tom’s newest chart.
 

Ian H

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Jan 24, 2005
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Re: C02 Charts

AV8TOR said:
Silly question, (but I also believe that no question is too silly)
I use a digital pH meter with 0.01 resolution. Is it safe to say you can interpolate between an indicated pH of 7.1 by averaging the difference between 7.0 and 7.2 on these charts?

The math does not seem to work though. If you use the chart with a kH of 3.5 and a pH of 7.0 and 7.4 to find a pH of 7.2
10.3-4.1 = 6.2, 6.2/2= 3.1, 3.1+4.1=7.2 yet the pH for 7.2 is 6.5.

This is from Tom’s newest chart.

Sorry AV8TOR but I believe that a question can be too silly.

You are lucky to have a meter with an 0.01 resolution, most do not, and rely on test kits that at best are subjective. The charts are a rough guide. If you want to strip out the none carbonic acid content and the none carbonates then your question would be more valid.

As to the math, the numbers equate but not in the context of the chart. The charts are for guidance to a theoretical ideal. The practical ideal may differ from this. Give me the practical any day.

So, without wishing to appear rude there is such a thing as a question that is too silly and I think yours could fit that catagory.

Ian
 

Greg Watson

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Re: C02 Charts

AV8TOR said:
Silly question, (but I also believe that no question is too silly)
I use a digital pH meter with 0.01 resolution. Is it safe to say you can interpolate between an indicated pH of 7.1 by averaging the difference between 7.0 and 7.2 on these charts?

The math does not seem to work though. If you use the chart with a kH of 3.5 and a pH of 7.0 and 7.4 to find a pH of 7.2
10.3-4.1 = 6.2, 6.2/2= 3.1, 3.1+4.1=7.2 yet the pH for 7.2 is 6.5.

This is from Tom’s newest chart.

It's a fair question ... I may be wrong here, but I think the charts are not linear ...

... and while I may not be certain of the correct "technical" or scientific term ... I think the term is either they are logrithmic or exponential (both these terms have different meanings) ... but to put it simply, you can't simply subtract and divide in half ...

To put it another way, the chart would normally be depicted in a graph, and the slope of that graph is not a linear straight line ... but a curve
 

Paul

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Jan 24, 2005
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Re: C02 Charts

I have a Hanna ph tester that is measures to 0.01, but it is only accurate to 0.2 TBO the one I have is rubbish (putting it mildly) and is never correct, complete waste of money, should have spent it on another liquid test kit
 

reiverix

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Re: C02 Charts

I wrote a quick program using the formula -

CO2 = 3 x KH x 10^(7-pH)

This is the result HERE.

I used a KH of 4. The numbers at the top are the CO2 ppm. Numbers at the bottom are pH. Changing the kH always produced the same shaped graph, just the CO2 numbers changed.
 

Liz

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Jan 23, 2005
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Re: C02 Charts

AV8TOR said:
Silly question, (but I also believe that no question is too silly)
I use a digital pH meter with 0.01 resolution. Is it safe to say you can interpolate between an indicated pH of 7.1 by averaging the difference between 7.0 and 7.2 on these charts?
QUOTE]

Don't use a chart -- use an equation. CO2 = 3* KH * 10 ^(7-pH)

where CO2 is in ppm, KH is in degrees. So if your KH is 6 and your pH is 7 then your CO2 is 18.
 

Tom Barr

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Re: C02 Charts

There are questions that are too silly, I'll ask them anyway:)
 

Ian H

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Re: C02 Charts

Tom Barr said:
There are questions that are too silly, I'll ask them anyway:)
Yes, but how would you respond to being asked a too silly question? You have far more experience in this area than me. :)

BTW I'm sorry if this is a too silly question about a too silly question. Sometimes the best response is no response.

Ian
 

Tom Barr

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Re: C02 Charts

Ian H said:
Yes, but how would you respond to being asked a too silly question? You have far more experience in this area than me. :)

BTW I'm sorry if this is a too silly question about a too silly question. Sometimes the best response is no response.

Ian

I'm not sure if you are aware I teach college Biology, I get asked silly questions everytime. Some students are full of them.
Other think they are way too cool. The silly ones are often some of the best, although obnoxiously correlated, questions.

Will adding PO4 cause algae?

That was a silly questions not too awful long ago.

Regards,
Tom Barr
 

aquabillpers

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Re: C02 Charts

The question was not silly, in my opinion. The chart was a bit goofed up, as Steve pointed out. One should be able to interpolate, since the functions are linear.

Bill