# Can There Be Too Much Co2 For Plants?

#### Joshaeus

Member
Well...can there be? I just tested my experimental 1 gallon jar and CO2 levels were at 90 ppm right after the photoperiod ended. I assume this would be lethal to most animals, but what about plants? (For those concerned there are currently no animals in the jar...)

#### -Mak-

Member
Are you injecting CO2? How did you test?

The atmosphere has nearly 400 ppm of CO2 and rising, so you're fine

#### Wraithen

Member
Atmosphere is measured by volume, we measure fish tanks by weight. I don't know the conversion offhand

#### -Mak-

Member
Wraithen said:
Atmosphere is measured by volume, we measure fish tanks by weight. I don't know the conversion offhand
To put it less confusingly, I mean that the air in general has 400 ppm. Atmosphere as in the layers of gasses surrounding the Earth ops:

#### Wraithen

Member
-Mak- said:
To put it less confusingly, I mean that the air in general has 400 ppm. Atmosphere as in the layers of gasses surrounding the Earth ops:
Oh I misspoke earlier. I meant the air we breathe is measured differently than the way we measure in the tanks. 400 ppm in the air is not the same as we would be talking about in the tank. We measure differently so we use a different scale

#### Joshaeus

Member
I used the relationship between KH, PH, and co2 to calculate my co2 levels. PH was 6 and KH was 3...the chart I used showed that this means my tank has 90 ppm of co2. I did not add any buffers to this tank.

#### Wraithen

Member
Joshaeus said:
I used the relationship between KH, PH, and co2 to calculate my co2 levels. PH was 6 and KH was 3...the chart I used showed that this means my tank has 90 ppm of co2. I did not add any buffers to this tank.
The problem with that chart is it makes assumptions about what you have for kh.

Edit to complete post:

The better ph method is to test your degassed ph weekly, and aI'm for a 1.0 drop in ph. Some people have water that according to that chart indicates 90 ppm co2 without injecting any.

#### -Mak-

Member
Joshaeus said:
I used the relationship between KH, PH, and co2 to calculate my co2 levels. PH was 6 and KH was 3...the chart I used showed that this means my tank has 90 ppm of co2. I did not add any buffers to this tank.
I think those charts are only meant to be used if you're injected pressurized CO2. Either way I find them to be highly inaccurate. CO2 is only 2-3 ppm in water naturally, without injecting.

#### Joshaeus

Member
How am I supposed to test co2 then?

#### -Mak-

Member
Wraithen said:
Oh I misspoke earlier. I meant the air we breathe is measured differently than the way we measure in the tanks. 400 ppm in the air is not the same as we would be talking about in the tank. We measure differently so we use a different scale
Oh, I see now. This makes sense because water is so much denser. I guess a more accurate way to emphasize the difference would be the rate of diffusion in water vs air, as air has a much higher CO2 diffusion rate

Joshaeus said:
How am I supposed to test co2 then?
If you're not injecting CO2, then the equilibrium of CO2 dissolved in water is 2-3 ppm. That'll be about what you have, unless there's some crazy amount of decomposition going on.

#### Wraithen

Member
Op has not indicated they are not injecting co2.

The two main methods of measuring disolved co2 in injected tanks is comparing baseline degassed water ph to injected ph. AI'm for a 1.0 drop.
The other method is to use a drop checker

#### Joshaeus

Member
I am injecting co2...

OK. I will try that. Thanks