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Best time to swap lights?

I am upgrading lights from (2) 300w Vipar Spectra to (4) qb120w, in a 2x3 tent.
Currently I have babies under 1 300w.
They just formed 3 finger leaves a week old.
My question is how soon can I switch to the ultra bright Quantum boards. I plan on 1/2 power, with light high as possible at first.
The QBs are so much brighter, I don’t want to shock or burn the girls.
Any suggestions are appreciated.


I’m not a led guy but the principles should be the same as hids. I think u will be fine where you can dim and raise the light.just slowly lower light so the girls have time to adjust;)


I run 4 of the 120’s as well…

I run mine like this:

Week 1 the seedling should be under cfl light

During Veg I would maintain a height of 20 to 24 inches with the lights turned down.

When transitioning to flower you want to still be at 24 inches but you want to start turning your driver up little by little every few days. You should let your plants start growing up towards the light until they get about 12 to 15 inches away.

So in flower, after the stretch, you want your lights turned up to 100% and at around 12 to 15 inches until harvest.


Sorry for the late reply but , thanks that really helps. i’ll try to post a pic.

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At the end of your flower cycle you may start to see some foxtailing. If you do, just raise your lights up or turn the driver down to lower the light intensity. Good luck!

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