Okay, maybe that title is a little sensationalized. This is hardly a smackdown – it’s barely a schoolyard slap fight – but I’m gonna stick with it because it’s so dumb that it made me laugh aloud when I typed it. Today I kicked off a new lil’ experiment in which I’m going to compare a 3000K vs. 5000K LED grow light.

The Plan

I have 2 space buckets (you can check out the build here), and in each bucket, I’ve got a single Vero 18 COB LED. The only difference between the 2 buckets is that one of the COBs has a color temperature of 3000K, and the other has a color temperature of 5000K. My goal for the experiment is to see what difference, if any, the color temperature makes on the growth of the plants, as they progress from the young fellas you see in the pictures below, right through into the fruiting stage (if I can manage to go that long with killing them). I will be running these on the same timer for 14 hours a day, and will water both buckets at the same time.

I admit, this isn’t a great experiment as I only have one pepper and one tomato plant in each bucket, but I’m hoping there will still be a visible difference despite my small sample size. If, after awhile, the tomato plants take over the whole bucket, I’ll take note of the peppers’ progress up to that point, then probably boot them out. Perhaps by then, I’ll have another couple lights to put the peppers under to continue the experiment.

The Parts

Here are the 2 buckets I’m going to be using. They are identical in every way, except for the COB color temperatures. Each COB is actively cooled by a CPU fan and is being driven at 1.4 amps by a Mean Well LPC-60-1400.


My friends are not going to have a clue WTF these things are.


These give my basement a very spooky orange glow.

The Participants

I’ve selected 2 “Mexico Midget” tomato plants and 2 Caramel Moruga Scorpion peppers for this grow. These plants were all started under the same lights in my main grow tent, and I tried to choose pairs that were most similar in health and size.

3000K vs 5000K LED Grow Light plants

Bitter rivals.


Mexico Midget tomatoes.


Caramel Moruga Scorpion peppers.


The 2 teams settled into their new homes.


What do you think will happen? Will the color temperature make a difference, or will the end result be the same? Make your predictions now so you can say “I told you so” afterwards!


  1. I’m betting you will be out of room in the buckets far before you will be able to get any definitive data, even with just the tomatoe contrary to the name thats still an indetemanite variety. Thats why the space buckets are usually centered around weed plants, (indica) that are topped multple times. You will be a slave to keeping that tomato plant watered in that 16oz cup once it’s roots get fully established. I hope you will keep their original lights over the plants even after they have grown out of the bucket to try and get some kind of measurable results. I’m guessing the ones under the 5000k will be shorter and at least have shorter internode lengths than the ones under the 3000k but you will have to let them grow for a while into the flowering phases to get some good measurable results, good experiment I’m definately interested in seeing the outcome of this.

    • LEDGardener

      December 4, 2016 at 4:04 pm

      I will definitely be transplanting the tomatoes up into larger pots as required. You can also keep adding “bucket tops” to continue to expand vertically as high as you want to go (picture a stack of 5 gallon pails, but only the top halfs of the pails). The space bucket founder himself posted a few pics of a cherry tomato plant in a bucket here (although it’s tough to gauge the size of the bucket – maybe it’s a garbage can), so it can be done, but will take work! He had written in another post that he used a glass top to force the plant to grow outwards, and also topped it. I have a feeling the peppers won’t be in there long at all before they’re completely covered, but I want to see how they grow from the super-early seedling stage too.

      As you say, if I run out of room, even with added bucket tops, I’ll just move them out of the buckets and into a bigger tent with the same temperature lighting, and more lights.

  2. And…

  3. For the moment I’m in doubt to get the 3000-3500 or 4000k led strips( samsung Q.serie) for growing.
    If I look @ the tech data I noticed that the difference in red spectrum for blooming is just a little bigger(1-2%max) for the 3000 and 3500 compared for the 4000. the big difference i see in the data is that the 3000-3500 produces less lumen/W output compared to the 4000k. According to my interpretation I would say the 4000k produces as a bonus just more blue spectrum compared to the 3000 and 3500. Is this interpretation correct?

  4. hello,
    2 quick questions.
    1. which paint did you use to paint the buckets?
    2. anyway to use the heatsink fan to make a carbon filter setup like an all in one?

    • LEDGardener

      January 1, 2018 at 4:17 pm

      I used a flat white spray paint. I’m not sure about the filter – I don’t think it’d be ideal because the heat sink is pretty much sealed outside of the bucket and is only removing hot air from the top of the heat sink rather than from inside the bucket.

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