3k or 4k CMH, 4 Plants Different stages

Hi guys,
So I Have a grow running at the moment with 2 plants that are 3 weeks old and the other 2 plants are 1 week into flowering, Should I use a 3k or 4k bulb? Running CMH. suggestions would be great!

cheers!

If used for Veg and Flower, 4k is often preferred.

3k is best for Flower only.

I use a 630 watt cmh with 3100k and am liking it for flower

4k

Cool, Maybe I'll keep the 4k running for 2-3 more weeks or so then swap over..

thanks guys!

is it ideal to keep the 4k running till the flowering initial growth settles?

I'm getting a 315w cmh myself is there a big difference with 3100k vs 4000k. I don't really wanna spend 50-100 dollar on another bulb. The package I bought is the 315w CMH Vivosun that come with 3100k bulb

XDRollingStone said:

I'm getting a 315w cmh myself is there a big difference with 3100k vs 4000k. I don't really wanna spend 50-100 dollar on another bulb. The package I bought is the 315w CMH Vivosun that come with 3100k bulb

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I just finished a run from start to finish under a philips 3100k bulb in a 315, plants loved it, they vegged nice and flowered even better.

3100 is fine for both

XDRollingStone said:

I'm getting a 315w cmh myself is there a big difference with 3100k vs 4000k. I don't really wanna spend 50-100 dollar on another bulb. The package I bought is the 315w CMH Vivosun that come with 3100k bulb

Click to expand...

Quite the difference. Less Stretch, more Ideal Spectrum for vegetation.. Ideal but dont stress. if you dont want to fork out the cash youll be sweet still.

you will like the CMH I recon. Brings out some nice oil and denser buds that the equivalent wattage of HPS.

Agree 3100k is fine for both, while the cmh light temp is a little high for me so that i finally go with led now .

Grow for fun only said:

Agree 3100k is fine for both, while the cmh light temp is a little high for me so that i finally go with led now .

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I'll be using it in a 3x2x6 tent you think it be too hot to run it in that tent

XDRollingStone said:

I'll be using it in a 3x2x6 tent you think it be too hot to run it in that tent

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I think you will at the very least need an exhaust fan to help release some of the heat

I went the entire run in that tent and under the CMH without exhaust, temps got as high as 82-83. Thats in a 4x4x7, i expect 2x3x6 will get a little warmer

Def need exhaust I ran my cmh in 3x3x6 and def need to vent air. I've run both and flowered and vegged under both. They are both really nice lights for either stage, I can say I think the 3100 helps finish a bit earlier.

its unwise not to have an exhaust with any light unless ur sealed room and AC id suggest.

I’m using a 41k... one thing I can say is mine seem to love it as well... I don’t believe you u could go wrong.... do you guys recon one runs cooler aa far as temp... that’s the only reason I see a need to JUST change...my tree looks like it has glitter oit at 5 weeks... I’m impressed... now the summer heat with the 315 is another issue... a fan and vent fan as well as a/c..I don’t see me JUST changing more less adjusting to it... jm2c

Don't be scared.
Veg'm under a 4k.
Flower under both!

TintEastwood said:

Don't be scared.
Veg'm under a 4k.
Flower under both!
View attachment 4350970

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Nice! I run mixed spec cmh bulbs too. No problem with heat in a hybrid loop system exhausting from grow room to grow and constant fresh cool air intake