Why use blue or red lights? Will any LED light work?

I’m hoping to chat with dbrn32.
I’ve been doing a lot of research on lighting, and I’m finding a lot of confusion. 1. With me just starting a new first grow, should I get a high quality full spectrum LED? Like the 4ft shop lights: Can I use a 4ft LED SHOP light for early seeding and growth.? Why would I want to use a mostly red or mostly blue light? And benefits? I see a lot of light say they can be used for veg and flower. Or most advertise this claim, Should be looking at a single LED that can be used for veg and flower? Since this is my first hydroponic grow, I will use all 4 5gal buckets but with 2 different strains. My plant area is 3’x5’. Will a 600-1000w LED light with power adjustments be too much for this set up?


Put the @ sign before Name to get their attention @dbrn32

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You are going to need enough coverage for 4 plants. Unless you go with a Quantum Board (recommended) you will need multiple fixtures to get the coverage you need.

LED’s are an incredibly misleading market and many of us, myself included, have been bitten by them. The thing you have to understand is first the marketing of the lights: if it says 1,000 watts it means it has, say, 100 ea. 10 watt LED’s. Fine so far but they are only driving the LED’s at 18 to 20% of their rated peak. So your 1,000 watt light is only pulling 200 or 250 watts at the wall–this is the important datum. Second; the LED’s used are early tech that is WAY less efficient than later generation LED’s. Third; the Blue and Red is simply cheaper to do than an actual 3,000K LED.

LED shop lights draw pretty low wattage (again, the important datum) like 25 watts or so. Not enough to grow cannabis I’m afraid.

There are some wonderful lighting choices out there but they start to get a bit pricey and it pays to look around and get good advice. @dbrn32 is our go to guy for all things light. And he’s wonderful to work within YOUR budget.

My story: I started with 3 Blurple lights and as my area increased I kept acquiring more blurple lights until I had coverage: 1,350 watts at the wall. I replaced that a year ago with diy Samsung EB strips in 3,000K, adjustable from 300 to 720 watts. My last grow, 3 plants, 5 1/2 months, hydro, 720 watts for the last 2 weeks only (most of the grow ran at 600) and pulled 2 lbs of flower from them. My electric bill went down $60 the first month I switched over.


You mentioned 3,000k. Is it measured the same as the hid lights for vehicles?The more k’s the more light intensity?

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Nope 7500k is more blue of a light 3000k is more reddish of a color. So the lower the k the more red spectrum will be in it. I have 3 autos under 2 qb 260w xl 3000k Right now so 520w. They love it they grew into crazy bushes. You can run the 3000k from veg to flower works great. These light deffinetally produce some serious light. hqdefault


You will need sunglasses


I’m happy to help you with lights. Red and blue leds will grow weed, no doubt. But the earliest designed led grow lights went that route because of the poor electrical efficiency of leds at the time. To make up for it, they tried to load up on the most photosynthetically efficient wavelengths. Which is where you get your red and blue, or commonly referred to as blurple fixtures. As time went on, increased technology made leds much more efficient, and newer light studies suggest there is more value in wavelengths outside of the blue and red ranges.

The term “full spectrum” means there is representation from every color in the par region. The par region is from 400nm to 700nm. That includes violet, blue, green, yellow, orange, and red. Anything truly full spectrum using colored leds has to contain at least 1 led of all of them all. However, just about all white phosphor color LEDs contain them all in a single chip. Light spectrum is important, but minor details in it aren’t really going to change much in a grow.

From there, it’s all about the efficacy of your lighting. The typical 4’ led shop light fixture you’ll get from home improvement store will have something like 4000 lumens printed on the box, then in smaller print somewhere tell how many watts it consumes, we’ll say 40 watts. So the luminous efficacy there is 4000/40 or 100 lumens per watt. We try not to get too focused on lumens due to how they’re measured, weighted to human eye. But that’s what they give us, so pretty what we have. Just for comparison sake, the higher end LEDs that you see the bigger price tag on, are capable of running over 200 lumens per watt. Breaking it down, it will take twice as power in big box store shop lights to get the same light intensity as a higher end horticulture specific fixture.

That pretty much leaves you at targeting proper light levels. The minimum recommended light intensity for flowering cannabis is a ppfd average around 600 umols per second. A horticulture fixture will give you the information to calculate this, but you have to kinda thumb eyeball using anything else. When I build fixtures, I like to try and get close to a ppfd average of 800 umols per second. That’s considered the point of diminishing returns on ambient co2 levels. It doesn’t always work out that way as there are limitations with voltage and current on all of the components. I can usually get pretty close though, just takes a lot of crunching numbers sometimes.


If you have the means, buy or build a Quantum Board. I started with a Viparspectra Par 700…and yeah, I grew weed. I picked at @dbrn32 ‘s brain last grow and built a QB. My yeild average more than doubled (adjusted for extended veg time). The nugs are way more dense…it has been an all around improvement and only a slight increase in power usage ‘from, to’.


All great advice! Thanks @dbrn32