CO2 ppm vs PPFD

I am wondering what the target co2 ppm should be if your light can only achieve 850 PPFD? I have head that there is a threshold where you will just be wasting co2 and the plants cannot absorb anymore if your light isn’t strong enough.

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Extra CO2 offers no benefit at 850 PPFD. You need to be pushing 1,200+ PPFD for supplemental CO2 to make any difference.


Thank you! Do you have any recs on an LED that can attain 1200+ PPFD? My current one listed that 1200 is attainable but after talking to them, they said their initial specs are not accurate. The highest I’ve been able to get to is 850 with the light 6” away from the PAR sensor. Disappointing to say the least since I already invested in the co2 system.

I get 1,100 PPFD from 3 HLG 135 Rspec panels above each plant. It is 390 watts per plant with Samsung LM301 diodes, and even that doesn’t get me there.

You can grow great cannabis by focusing on the basics (good soil, proper watering, management of pH and PPM, good lighting,…) CO2 is an advanced method that very few experienced growers use.

What light are you using?

To hit 1,200 PPFD, you are going to have to have 450+ watts of quality lighting per plant. Quality lighting costs a little more than $1 per watt, so you are looking at a $500+ light to use CO2, not to mention that there are other environmental factors that need to be run to their limits when using CO2.

You can grow great plants without CO2. Here is one of them.


Beautiful plant!!


This is great information! I appreciate it. My current light is 720 watts, but it seems more focused on spectrum control and was $1500. It is the ThinkGrow H-Plus. I was a bit surprised when they told me I am probably at my max at 850. I’ve heard that co2 is less important with LED and everything is looking great with my first run, regardless. My nutes/coco seems dialed in. I cannot complain with how they look. I was just hoping my co2 would bring it to the next level. Have you heard anything about Grandmaster LED? Thanks!

I haven’t, but their website states that they use LM301h diodes, which are top notch. Something doesn’t seem right if you can’t hit 1,200 PPFD with 750 watts from LM301h diodes.

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My current light is the ThinkGrow H-Plus, which I’m having issues with getting above 850ppfd. I’m just curious about the GM lights. I’ve heard great things about GM.

Got it. I expect your current light is built with LEDs that are less efficient than the LM301h.

I would compare their products with those of Horticulture Light Group. HLG is well-known with a great reputation. I’ve never heard of GM and am skeptical.

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Just checked my current light specs. It says they use Samsung LM301B and Samsung 351H (660nm)V3. Still learning so not sure if this was an obvious sign. I will look into HLG too.
I was just hoping that this light would achieve some different outcomes. I guess I need to research the diodes more.
You have been very informative, so thank you very much! I thought I researched everything very well, but it seems like I need to educate myself even more. :pray:t3:

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