# The best time for CO2?

Discussion in 'Advanced Growing Techniques' started by Chronitron, Jun 16, 2008.

1. #1
When is the best time to give plants CO2? When the sun is out or when it goes down? I'm going to open a tank in there but I want to do it at it's optimum time. Any help is appreciated.

Thanks GC!

2. #2
I believe CO2 is best used by the plant at peak sun/temp times. Plants can withstand hotter temps if there is more CO2 in the air.

I've got a question about CO2 as well: Is CO2 lighter than air/Does it float up, or sink down?

3. #3
I think it sinks down. Thanks for that. I was definitely about to go open it now that the sun is going down. I'll wait until tomorrow.

4. #4
Plants don't use c02 when the lights are off so 1500PPM during the lighting period is optimum but not practical unless a total sealed grow is done.

So some cycling of lights on and fans off with added co2 is your best bet,BTW when your ventilation is off during the co2 period your tempt can go to 95F. with no ill effects using all the co2.

5. #5
Co2 will be heavier than the air we breath.

6. #6
how much co2 will a 20oz bottle filled half up with water, 2tbls yeast, and about 1/5th of sugar to water make?

7. #7
Via stoichiometry,

Sugar is c6h12o6 / mol. Density is 88 kg / m3 (or 88 g/L). Molar weight is 180.18 g/mol. 1/5 of an 20 oz is 4 oz, which is 118.29 ml. The chemical equation describing the reaction is c6h12o6 +02 --> c2h50H + 4c02 + h20. Therefore the stoichiometric ratio of completed fermentations will be 1:4, molar. You are starting with .11829 L, which is 10 grams. This is .0555 mol. At SATP, one mol is 24.6 L. This means the gas you have created takes up 1.37 L. As you can see, you're NOT really doing much. If you check wikipedia, 1% seems to be the amount they recommend. Normally C02 is like
[SIZE=-1]0.0314%, by volume. So, unless your room has a volume of 100 ft^3...you probably aren't doing much.

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8. #8
Much discussion has been done on this and in the end it has shown to be less than productive as it only temporarily raises the PPM to 400-500 from the 300ppm in room air.

Optimum co2 PPm is 1500 or more,although a chemist has said the product co2 boost is different and will put out some real usable PPM although i have not tried it.