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Old 08-02-2019, 08:59 AM   #1 (permalink)
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Default Everything you want to know about CO2 and Aquatic Plants video

I'm planning to do a youtube video explaining CO2 & aquatic plants.
I don't have time now but might have some time soon. First I need to write a script for it. If any of the experts here want to contribute, please do.

I'll write the script and post it here. I'll start with an outline.

1. CO2
a. Atmospheric CO2 at 400, 407 ppmv. Explain parts per million by volume
b. CO2 in water: Explain partial pressure and ppm by weight or mass (mg/L)
c. Sources of CO2 in water, atmosphere & animals & decaying organics in the sediment (bacteria)
d. CO2 form carbonic acid in water, lowering the pH. Include CO2 speciation, CO2, H2CO3, CO3. Show speciation/pH concentration chart. Introduce the CO2,pH,kH chart, carbonate hardness, CO2 = 3 KH 10(7-pH). Remind that it only works in a pure water, with a little baking soda to control kH. A drop checker is a good, cheap approximation of CO2 concentration. If you need an accurate reading, it's best to have a CO2 sensor in the water or above the water using Henry's Law.
2. Plants
a. CO2 in water, a liquid, slower in diffusion, that's why plant need more CO2 and leaves physiology change to adapt to get more CO2. Compare that with terrestrial leaves.
b. CO2 function in plants
c. Usually aquatic plants can use HCO3, & CO3 too. Different enzymes are responsible for converting them to CO2.

Last edited by mistergreen; 08-03-2019 at 03:46 PM..
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Old 08-02-2019, 04:16 PM   #2 (permalink)
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Default Re: Everything you want to know about CO2 and Aquatic Plants video

Daily consistency when using CO2.

Measuring pH drop. De-gassed vs. CO2 when lights on.

Two things that came to mind.
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Old 08-02-2019, 08:48 PM   #3 (permalink)
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Default Re: Everything you want to know about CO2 and Aquatic Plants video

Ah, co2 forming carbinc acid in water, lowering the pH is good point to mention.
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Old 08-03-2019, 06:22 AM   #4 (permalink)
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Default Re: Everything you want to know about CO2 and Aquatic Plants video

Not just lowering pH but how many will target a 1.0 drop in pH whuch is approximately 30ppm of CO2.

The time delay when using a drop checker can be an issue.

Bubbles per second means very little, just confirmation of flow.

How to properly degass tank sample, air stone for 30 minutes.

Still thinking of more!
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Old 08-03-2019, 06:50 AM   #5 (permalink)
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Default Re: Everything you want to know about CO2 and Aquatic Plants video

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Originally Posted by Maryland Guppy View Post
Not just lowering pH but how many will target a 1.0 drop in pH whuch is approximately 30ppm of CO2.
I've done some reading on this. It all depends on the water chemistry, kH, pH... It works well in a controlled environment/ pure water environment like a drop check but isn't reliable in an lake/pond or planted aquarium.

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Old 08-03-2019, 08:56 AM   #6 (permalink)
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Default Re: Everything you want to know about CO2 and Aquatic Plants video

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Originally Posted by mistergreen View Post
I've done some reading on this. It all depends on the water chemistry, kH, pH... It works well in a controlled environment/ pure water environment like a drop check but isn't reliable in an lake/pond or planted aquarium.
When the pH drops in aquarium water, as CO2 is added, the pH drop is an accurate measure of ppm of CO2, because no other parameter in the water has changed. If the water is allowed to outgas the CO2 until it is in equilibrium with the CO2 in the air, and if that leaves you with about 3 ppm of CO2 in the water, then the ppm of the tank water when it has CO2 added is 3 times 10 raised to the drop in pH power. So, if that drop is 1.0, there is about 30 ppm of CO2. If it is 1.2, there is about 50 ppm. (Note that this isn't accurate beyond about 1 significant figure, so it is 50, not 47.5 ppm.)
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Old 08-03-2019, 10:03 AM   #7 (permalink)
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Default Re: Everything you want to know about CO2 and Aquatic Plants video

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When the pH drops in aquarium water, as CO2 is added, the pH drop is an accurate measure of ppm of CO2, because no other parameter in the water has changed. If the water is allowed to outgas the CO2 until it is in equilibrium with the CO2 in the air, and if that leaves you with about 3 ppm of CO2 in the water, then the ppm of the tank water when it has CO2 added is 3 times 10 raised to the drop in pH power. So, if that drop is 1.0, there is about 30 ppm of CO2. If it is 1.2, there is about 50 ppm. (Note that this isn't accurate beyond about 1 significant figure, so it is 50, not 47.5 ppm.)
Yeah, I wish it was that simple but chemists I've seen online are saying it's not that easy. The CO2 ppm depends on the water chemistry. It for sure works with pure water.
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Old 08-03-2019, 11:44 AM   #8 (permalink)
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Default Re: Everything you want to know about CO2 and Aquatic Plants video

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Originally Posted by mistergreen View Post
Yeah, I wish it was that simple but chemists I've seen online are saying it's not that easy. The CO2 ppm depends on the water chemistry. It for sure works with pure water.
It isn't accurate to use KH and pH to measure ppm of CO2, because of the things in the water that affect pH and KH, other than CO2 and carbonates. But, when you use just one sample of water, and measure the pH with only the ppm of CO2 varying, it is as accurate as any of the other hobbyist methods for measuring CO2. The only part of this method which is questionable is the use of 3 ppm as the "no added CO2" ppm of CO2 contributed by atmospheric CO2. A 20% error in that 3 ppm number means a 20% error in the derived CO2. Chemists who don't think this method through are not qualified to make statements about the accuracy. (My opinion, of course.)
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Old 08-03-2019, 02:08 PM   #9 (permalink)
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Default Re: Everything you want to know about CO2 and Aquatic Plants video

I found this case for seawater & freshwater

http://www.soest.hawaii.edu/oceanogr...2012/CO2pH.pdf
Notice how CO2(aq) and other speciation concentration change depending on pH.


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Old 08-03-2019, 03:19 PM   #10 (permalink)
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Default Re: Everything you want to know about CO2 and Aquatic Plants video

I just read an post, luckily, usually aquatic plants can use HCO3, & CO3 too. Different enzymes are responsible for converting them to CO2.
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