I see a 20,000k (color temperature) 12 watt LED E27 bulb designed for coral, aquariums and such. 7000k is supposed to be full-spectrum light, I hear. So, I imagine a 20,000k would be even more full-spectrum.

I realize 12 watts isn't going to be as powerful as sunlight.

Anyway, how effective is this going to be as a grow light for vegetables compared to blue and red LED 12 watt grow lights? Will it have infrared and UV rays?

Here's a link to the product if you're curious. (select the 20,000k option)

They also have a 10,000k bulb.

Since they're marketed for helping coral to grow, I imagine there's more to it than merely giving the appearance of 20,000k light, but I could be wrong.

EDIT: I ordered one bulb, and a blue one from the same seller. So, I guess I'll be able to answer this question within a month or two (granted there's no red in the light to compare in that regard).

  • functional as a grow light to grow what? and how far away from the plants would they be placed?
    – kevinskio
    Dec 27, 2014 at 2:39
  • @kevinsky They would be used for such as tomatoes, peppers, tomatillos, cucurbits, arugula, purslane and dark red lettuce. Suppose you had one light per plant, and each light was a couple inches from its plant. But keep in mind, I don't just want to know how well it'll work as a grow light, but how well compared to the standard red/blue LED grow lights of the same wattage (which have wavelengths of such as 660, 640 and 400-something). This is not for commercial purposes. The plants are in my bedroom. Dec 27, 2014 at 4:02
  • @Shule: At that wattage, you'd be better off with about 3-4 lights per plant. 12W is not much and it sounds like your stretching the coverage of one light further than is going to work.
    – Enigma
    Dec 30, 2014 at 21:21
  • The bulbs arrived, today (the 20,000k one and the blue one). They are actually quite bright. The bulbs are tiny. Unfortunately, I'm not sure which one is the blue and which one is the 20,000k. They both look similar in color. Edit: I think I figured it out with a side-by-side comparison. Now, I just need to test them out on my plants. Unfortunately, I still need some sockets (lamps) that I can position above them, but I should be able to get some next week or so. Jan 21, 2015 at 0:19

3 Answers 3


A 20,000°K lamp will have peak output at 145 nanometers (Wien's Displacement Law). That's hard ultraviolet. It will hurt your plants. 10,000°K still peaks at 290nm, UV. You want a lamp with a far redder color temperature. Here's a nice graph of the wavelengths plants like: enter image description here

See the page Light and Plants

  • So, what you're saying is I could use this light to get super hot peppers, so long as I don't overdo it? (That is, since stress to peppers, including from the damage caused by certain UV rays, increases the capsaicin.) I'm guessing it has longer-wavelength UV rays than 145nm in it, too. Dec 28, 2014 at 1:32
  • 1
    @Shule yeah, more intense uv will increase the capsaicin levels, as will dryness, slight nutrient deficiencies, especially iron, and other things.
    – J. Musser
    Dec 28, 2014 at 13:08
  • @J.Musser: When you say dryness, are you referring to soil moisture or air humidity? Or both?
    – Enigma
    Dec 30, 2014 at 20:55
  • @Enigma both, but especially soil moisture, as that's more stressful when lacking.
    – J. Musser
    Dec 30, 2014 at 21:11

"Cool White (6000-6500k) Warm White (3000-3500K) Natural White (4000-5000k)"

This is the section you should be looking at for a grow light. The best light range for indoor growing is between 2700k and 6500k depending on what you are trying to do. Blue light (5000k+) is used for vegetative growth and red light (2700k+) is used for flowering. When you have a full spectrum light such as the one you linked, you'll get growth and flowering, however the plants tend to mature faster and it's an overall loss. Your best bet would be to buy two lights, one of each spectrum and when you're ready to switch from growth to flowering just change out the lights.

To answer your question: Yes, it would work but it wouldn't work as good as a light of the correct spectrum.


Here's another Kelvin spectrum:

enter image description here


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