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Arcadia T5 54w Dragon Reptile Bulb. 46 inch. Most powerful UVA/UVB bulb available.
Use them at `108w x 4 x 4 @ 18 inches from canopy top. Experiment first with 2 feet, and slowly bring to 18 in. Will penetrate 3 feet. Will also blind you if you muck around. Work only when lights are off.
Use 2/3 of the time lights are on, in Veg/Flowering. That's what Ive had success with anyway.
If vegging 18 hours, use the UVA/UVB 12 hours.
12 hours flowering use for 8 hours.
I run them 2 hours after HID come on, and turn them off 2 hours before they HID go off.
Veg I wait 3 hours before activating UVA/B, and turn off 3 hours before lights out.
I use 1 x 1000w Hortilux Superbulb for each 108w UVA/UVB in 4 x 4.