Try 10 min per day and see what effect it has on the plant over a week or so. Maybe bump it up to 20 min and repeat. Watch for brown/burning on the buds and leaves closest to the source of light. Back off if need be. Use caution as it will fry your plants if you don't watch it closely.

I'm in the same boat with my uvb bulb. Mines designed to be used like 3 feet from the canopy. Height restrictions force me to leave it on for just a few hrs per day. I have yet to optimize it though.

@av8ersteve

What light frequency range is the UV on that light? For the UV part of the light to promote resin production, it should be UVB light at roughly 310nm. I believe that SpiderFarmer UV/IR supplemental light is providing UVA at 380nm and above. Is the light capable of running UV and IR at separate timing?

I have 2 sets of Grower's Choice UV/IR addon bars on my two ROI-E720's. My UV is UVB and I can run with UVB and IR on, UVB only on, or IR only on. I cannot run the UV and IR at separate timings without manually making the change daily. To get the most out of supplemental UVB light, it should come on for a short time in the middle of the light cycle ... and increased gradually so that at peak, your plants are receiving a couple of hours of UVB. IR when used with far red, should be used right at lights on and right after lights off (google Emerson effect).

As you see, the way these lights are made do not allow you to use the different light frequencies on separate timings. So, to get the most out of the light frequencies requires different lights on different time schedules.

Verdict - Return the Spider Farmer UV/IR light. It cannot do what it claims to do. You're better off running without it.

As others have said, wavelength with uvb is key. I never heard about using IR, but I use mine with a timer for the middle of the light cycle. T5 or t8 bulbs are the only way to go for uvb. Led's are not there yet in efficiency or cost, but they sell uvb bulbs that offer uvb and uva, which should work together much better.




Also, I know uvb is in our sunlight year round, but I don't know of any benefits to using in veg cycle. Mostly flower.

And keep it about 32"+ above canopy.

Powerstroke said:

As others have said, wavelength with uvb is key. I never heard about using IR, but I use mine with a timer for the middle of the light cycle. T5 or t8 bulbs are the only way to go for uvb. Led's are not there yet in efficiency or cost, but they sell uvb bulbs that offer uvb and uva, which should work together much better.




Also, I know uvb is in our sunlight year round, but I don't know of any benefits to using in veg cycle. Mostly flower.

Click to expand...

Far red and IR is used differently than UVB and that might be why you haven't heard of it in conjuction with UVB. It's convenient for a manufacture to combine the light frequencies together and then market them as an improvement to a traditional grow spectrum.

Far red and IR at sunrise/sunset have the ability to influence changes between day and night which allows your plants to get to "sleep" up to 2 hours sooner and "wake up" more efficiently. This is why outdoor grown cannabis usually starts flowering once daylight hrs fall under 14 hrs. Google "Emerson Effect and cannabis" for more information.

These little differences is why I see tune-able spectrum as the future in grow light science because these spectrums do work when used at the right time in the daily photo cycle. We're already seeing it being used in some of the high end lighting. It's a matter of time before we see more of these lights being offered at lower price points.

I only use it in flower. Starting week 5 of flower. Start with 2 hours. Week 6. 3 hours. Week 7 and on 4 hours.

I do 15 minutes on 30 minutes off. But I set it up in the middle of the 12 and 12. Say my timer for my lights is 9 to 9. From 1 to 5 I use the uv light.