How do you monitor CO2 Levels?

[Jur4ik]

In Germany it must have been Dennerle

[plantbrain]

Originally Posted by Orlando

Not sure why folks still use that chart.

It can work if there's no interference.
DC's have a trade off.

I use pH and visual cues, calipers on the needle valves(Nupro makes some nice easy to reference handles) mostly myself.

I also am patient and slow to adjust the CO2. This prevents over gassing and stressing any fish. I add enough till I need no more.

Regards,
Tom Barr

[shayf]

Originally Posted by Supercoley1

Some people even think that a 1Ph drop is accurate. This is only if you have a specific KH. 30ppm will drop a different amount of Ph dependent on the KH within the tank so even this cannot be used.

I use a DC and a pH controller, but acctually, this one (for me) is the most accurate way to know my CO2 level, and I check it that way, once a month.

Assuming that water standing for 24 hours (at 1ATM and in room temperature) contains exactly 3ppm CO2, it will always be 1 degree pH difference to go to 30ppm CO2, no matter what is the KH.

There is a simple formula to calculate the exact CO2 level form the pH difference.
This formula is based on the KH/pH/CO2 formula -(CO2=3*KH*10^(7-pH)), and it goes like this:

Assuming X = Standing 24h water pH - Aquarium water pH
CO2=3*10^X

Example 1:
Standing 24h water pH = 6.83
Aquarium water pH = 5.76
X = 6.83-5.76 = 1.07
CO2 = 3*10^1.07 = 3*11.75 = 35.25ppm

Example 2:
Standing 24h water pH = 6.50
Aquarium water pH = 5.50
X = 6.50-5.50 = 1
CO2 = 3*10^1 = 3*10 = 30.00ppm

Example 3:
Standing 24h water pH = 6.50
Aquarium water pH = 6.10
X = 6.50-6.10 = 0.40
CO2 = 3*10^0.40 = 3*2.51 = 7.54ppm

Can someone please disprove it?

[Anti-Pjerrot]

Easy - In the aquarium, any acid present other than CO2 will influence that equation

[shayf]

This is exactly the reason this test came up!

In this test, the specific pH of the water is irrelevant.

1. Test the pH in the aquarium.
2. Take a glass of water from the aquarium and let it stand for 24 Hours.
3. Test the pH in the glass.

The difference in pH is the only thing that matters (!), because the difference in pH is derived only from the change in the CO2 concentrations and because we know that water in 1ATM contains exactly 3ppm CO2 (the water in the glass after 24 hours), it is easy to calculate it.

[Pedro Pinto]

Drop checker and pH tests

Best way to control your CO2 levels

[Shadow]

Originally Posted by shayf

we know that water in 1ATM contains exactly 3ppm CO2

I didn't know that water at 1 atmosphere contain 3ppm

[shayf]

Water that are at equilibrium with the air, at 1atm and in room temperature (20 to 25 degrees Celsius) have 3ppm CO2.

Actually, 3ppm is the avrage for co2 concentration in water all around the world (although it can be between 1-3ppm at different atmospheric pressure)


Something to read:
Carbon Dioxide + Control of Colloid Stability through Zeta Potential - Chapt 14 part 1

[Big Dog]

I read my Co2 checker that I got from ?GreenLeaf.com. I love the thing. It looks so nice in my aquarium all so.

[Garuf]

I use a mixture of watching the drop checker, fish and plants.

If people are obsessed about CO2 levels (not sure why they would set an arbitrary figure for every tank when every tank is different and has different requirements but say they are) would it not be possible to make a hybrid dropchecker/ph monitor by sealing the ph meter in the 4dkh water of a drop checker separate from the tank water and then setting the co2 to come on/off when the drop checkers ph fluctuates to levels that would equate to lime green? That way not only is the ph meter effectively just giving a reading of what you're injecting but it also would be immune to the effects of acidic compounds in the tank water? Correct me if I've miss understood the principle but to me that strikes me as the easiest way to ensure the co2 levels are in theory always the same.

[shayf]

Originally Posted by Garuf

If people are obsessed about CO2 levels (not sure why they would set an arbitrary figure for every tank when every tank is different and has different requirements but say they are) would it not be possible to make a hybrid dropchecker/ph monitor by sealing the ph meter in the 4dkh water of a drop checker separate from the tank water and then setting the co2 to come on/off when the drop checkers ph fluctuates to levels that would equate to lime green? That way not only is the ph meter effectively just giving a reading of what you're injecting but it also would be immune to the effects of acidic compounds in the tank water? Correct me if I've miss understood the principle but to me that strikes me as the easiest way to ensure the co2 levels are in theory always the same.

The principle is very nice, but practically speaking, it is almost immposible to implement .

The main problem is the time it takes (two hours or so) for the reference solution to get equalize with the CO2 level of the aquarium.
In that time, the controller will not stop to infuse CO2 and when it will stop it will be to late (CO2 intoxication).

In theory, the only way to succeed in this method, is to build a small compartment around the tip of the pH probe, wich contains a very small amount of reference solution and sealed with a permeable membrane (so CO2 will pass through but water don't). In this way the time of the equilibration will be faster (although not immediate).

From my experience, it is (very) impractical.

Originally Posted by Garuf

...(not sure why they would set an arbitrary figure for every tank when every tank is different and has different requirements...)

You are absolutely right about that!

CO2 should be treated as any other fertilizer and the dosage should be according to your specific needs in your specific tank.

To address this issue, i use different dKH solutions in my drop checkers to reflect the levels of CO2 I need.

For example:

In my high intensity lighted (540W of T5), highly fertilized (20-2-25), densely planted, high-tech tank, I want to keep 45ppm of CO2, so I put 6dKH water in the drop checker.

In my CRS tank with slow growing, low-tech plants, I want to keep 15ppm of CO2 (this little critters are very sensitive to CO2 and fertilizers), so I put 2dKH water in the drop checker.

and so on...