Dreaming - co2 feed for 2X2 flower?

Say I’ve got a 2x2x8 space, exclusively for flowering, with a 600w hps.
According to the man, Bergman that is, more light is better IF you’ve got co2 to back it up.

What should I do?

some searching will reveal this is a waste of money in a small tent, Co2 is for large grows with very high PAR lighting, above 800

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If you are in a grow tent then in order to get good air flow you likely have intake and exhaust fans which would pull out the CO2 anyway. Without the fans you risk mold if humidity gets too high or temperature problems from the light heat in the small space.

You will get a better payoff with good soil / Pro-mix etc, the best lighting you can afford and good nutrients. (I use General Hydroponics and Pro-mix)


I’m thinking even with co2 it wouldn’t be a very efficient grow. A 600 is ideal light for a space 3 times the size. It’s not enough square footage to produce enough to justify cost of running light that big, co2, and maintaining temps while keeping co2 in the space.


Thanks but you guys just aren’t helping.
I’ve got excellent ventilation - tapped feed & return to central hvac system.
Return has a strong cylinder 6" duct fan inline.

I know 600W is too strong for a 2X2. That’s kind of the point.
I also know that high levels of co2 in the house is dangerous if not contained.
I think I can deliver enough co2 to accommodate the 600W but not be harmful.

How can I make a correlation between co2 delivery & par?
Can I utilize the 600W in a 2X2 area by adding co2?
If so, how do I do it?

I don’t or haven’t ever run a 600, so I’m not familiar with radiometric output on them. Do you have ppf data for your light?

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I don’t have one right now. I’m trying to determine whether or not it’w worth it.
thanks for your help.

I’m getting that you’re thinking the light won’t stay contained?
In such a tight space the extra light won’t make it more intense than say, a 400 (my current one)?
The 2x2 is covered with mylar - if that matters.

It’s not. I don’t have data on your light, but I will share what I do have.

A Phillips green power 600watt hps bulb has a ppf of about 1100 umols per second. In a 2x2 that’s a ppfd average of about 3,000 umols per second.

The information I have on recommended light density levels suggests that on ambient co2 you hit point of diminishing returns with a ppfd average of around 800 umols per second. Light saturation levels on ambient co2 run around 1000-1200 umols per second ppfd average. Boosting co2 can absolutely change that, to some extent. But even taking co2 up to something like 1500ppm light saturation levels are seen around ppfd averages of 1400-1600 umols per second.

Maybe your light isn’t quite that good, and there’s some wiggle room within me not having most recent or accurate data. But I’m sure I’m not off by double. It’s simply just exceeding the capability of a plant or plants that size to produce. The cost of running the equipment won’t pay off in what the area will yield.


I see. Thanks for the research. I was looking but still haven’t found it.
So I would have to maintain co2 levels to toxic heights . . .

That very clearly answered my question.
Nope, no 600 + co2. I’ll stick with the 400.
Now I’ve gotta find a good ballast that won’t throw rf everywhere.
Thanks again, so much.

this ending statement is all that was needed.!!
but u did an excellent job explaining why 150 wpsf is not good.!


yes, and still have huge costs in getting all the equipment to set that up.!

a 400w HID is still too much for your space,
look into one of these kits…
this light will probably do about what your 400w HPS.!!
or 2 of these if u want a chit ton of light…


Thanks for your response.
The 2 lights you suggest are about double the price of a 400w hps ballast.

I quote from the first one:
“Equivalent to 250 Watts of HID power”

With the second one I really have no idea what I’m looking at.
I’m seeing ‘advice’ but no real specs except:
“B-288 V2 - Lamp Efficacy with LM301B: 2.40 µmol/J.
What does that mean?

Also, the cost of 2 of these is prohibitive for my use.

I’m intrigued by the whole LED/COB thing but it’s expensive.
I’m having a hard time getting any practical information.

As you pointed out in another post, advertising these days is a long way from ‘reliable information’.
I’m having trouble finding the facts.

Why are these lights superior to a 400W hps digital ballast (which I agree is a lot for 2X2).

Would you be kind enough to share your source?
I’ve been looking for something like that for some time.


WOW! Thanks. This was very informative.
and she’s cute!

This was also very helpful:

They stated that they started with grower reviews on results of PAR/CO2. I didn’t see those results (not scientific anyway). But, the study they did only measured light.We could assume a control of co2 @ ambient but I don’t see anything more.

I learned a lot from it. The vid was fun.
Did I miss something?
Maybe a different article?

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Did you look at charts? 1500ppm is 3-4 times my ambient co2

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Ya know, I did see that - guess it didn’t register (I must be stoned :-/ or old).

250-350ppm: Normal background concentration in outdoor ambient air
350-1,000ppm: Concentrations typical of occupied indoor spaces with good air exchange
1,000- 2,000ppm: Complaints of drowsiness and poor air.

So yea I see, the levels they were testing at are toxic.
They said flower weight tapers off @ around 1200 PPFD.
Strangely, HPS produced 12% less Active Cannabinoids, presumably at any intensity.
I wish they tested using control light & variable CO2 levels.

OK, so how did you determine how much PPFD a 600W light will produce in a 2X2X8 space?
I’d guess that it’d be pretty uniform all over the top of the canopy.
I’ve learned that my 400W light can be about 20" from the tops before they’ll start to burn.
And again, thanks a whole lot for all your help.

I’m not trying to be a pain. Sorry :confused: I’m just trying to get this figured out.
This doesn’t make sense to me:
“ppf of about 1100 umols per second. In a 2x2 that’s a ppfd average of about 3,000 umols per second.”
Wouldn’t ppfd (photons on plant) necessarily be lower than ppf (photons out of light)?

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Mylar? Hmm. It looks like you figure the plants will end up with double what the light will produce due to reflection?
That makes sense.

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Photosynthetic photon flux density is nothing more than light per square meter. 2x2 isn’t far from 1/3 meter squared. Assuming you keep light in space anyway.

It would make more sense if you put same light in 1m x 1m tent. Then your ppf is 1100 umols per second, your ppfd average is 1100 umols per second per meter squared.

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