UV spectrum importance for indoor grow lights

How important is having UV light in your indoor grow tent?

1 Like

I don’t know, but I like experimenting. :joy:


Welcome freind.
Idk much from experience but science seems to favor it dose indeed help bring out colors, terps, and oils.
I’ve been considering ordering 2 uv-r bars for my Growers Choice Roi-e720 but just haven’t yet…


How many watts is the add on bars you got?
The Growers Choice bars are 10w total and plug into my light for power.
They are about $200, but its the super low watts that I dont understand.
Will only 10w worth of uv and ir really be enough for a 700w light :thinking:


The bars are 30w apiece, it’s a mix of FGI and gavita, all we’re around $150 I think. The gavitas have a heavier heat sink and fit the length of my light better, FGIs are a little longer. Both same numbers of chips.


I have a 4x4x6 tent I will be lighting with a Vivosun VS2000(200w) and a 1000w Yansun (500w actuality)
I am planning 2 photos on one side and 4 autos on the other. The two lamps I have do not have UV. After some research I have been contemplating getting this and hanging it right in the center of the tent in between the two main lamps.

Or fix it at the top of the tent? Above the main lamps?

380-800nm? That’s basically the full spectrum of visible light.

For our uses what you want is a straight UV-A fixture
UVA is between 300-400nm.
UVB can have some benefit in small doses but longer exposure can cause some damage to the plant.
UVB is for reptiles.

I’d pass on that light and find a dedicated UVA light like those available from Forever Green Indoors(FGI) or HLG.
I prefer the FGI version to the HLG version - which is saying a lot as HLG sells incredible lights!

Oh hey - Welcome to the community!

1 Like

Thank you so much! So you definitely believe UV makes a big difference?

1 Like

Oh yeah - it attacks a plant the same way it attacks us. Just as we tan to reduce the absorption into the skin the plant produces more trichomes, resins and oils as a defense. It just happens that that’s the part of the plant that contains the highest concentration of THC.
More of one equals more of the other!
I have UVA in both of my tents.

1 Like

Will one of these work? Hang it inbetween the two main lamps? Or fix it to the top of the tent to spread it better?

1 Like

Yeah - I have 2 in my 4x4 but just because I like symmetry. LOL!
I’d mount between the lights at the same level. I run mine with my mains from start to finish with the grow, some only use it during flower.
I just figured there’s UVA in the spectrum all the time so if my point is to reproduce the spectrum of the sun as closely as I can why would I turn it off? The sun doesn’t!

I have the small version of the HLG in my 2x4 -


I have decided to go with better lights. Thoughts on this for an all in one light solution for my 4x4x6 space?

1 Like

Ever since i added my hlg uv bar to my 260 xl ive gotten a pretty significant veg and trichome size boost iits a shame that only half is getting full use of it but it’s better then nothing

1 Like

I do like the specs on those new Mars hydro lights, they’re making some real nice lights these days

1 Like

For a 4x4x6 space, would you think the extra $250 to go with this HLG set up is worth it?


HLG will take my vote over Mars Hydro any day.
I will also vote for KingBrite (cheap China-made alternative) and Green Beams (obscure US lights) for days before I recommend an MH or a Spiderfarmer to anyone. Don’t get me wrong, they’ll grow you some weed. But HLG, KB and GB will grow you better weed every time.

Edit: if you can find that RSpec on HLG’s website direct, DUDE should be 10% off. If you can find it refurbished, REFURB makes it 20% off the refurbished price.

I have the 650 Rspec refurbished. It looks brand new, minus one screw mounting the driver was obviously replaced.

1 Like

This is what I could find on Yansun 1000w grow light. It is from Home Depot. It consumes 150 watts and uses old generation Samsung LM281B diodes. Its price reflects its low efficacy and outdated technology

FWIW - I would put UV supplementation in the advanced grower and exotic categories. Your thoughts about upgrading lights is a much much sounder course to take.
HLG has some great lights. I have several of the 260 rspecs (288 QB). Having a short tent of 6’ the light’s hanging height is very important. HLG specifies: Recommended Mounting Height 28-36 inches above canopy.

So this would be my ideal light set up in my 4x4 tent? Can I start with the lights i currently have and switch to the HLG set up when I get it? It will be about a month before I can procure this HLG set up.

Also seeing as how I am growing photos and autos… would it be more ideal to get 2 hlg 300r’s instead of the one 600r?

1 Like

Returning my cheap lights and getting an Hlg Rspec with a Uva supplement bar. Aldo getting a taller 7ft tent. Thanks for the advice.

1 Like