Yellow sticky traps for fungus gnats have been a way of life for me and my living soil grow, until now. I realized that the two T5 3000k tubes in Nanotech single fixtures I had slid on top of my pots pointing upward as under canopy lighting were doing an even more effective job than the sticky traps were. The gnats are attracted to the UV from the tubes which is mostly absent in my LEDs. Once attracted they quickly succumb to the heat. After running the lamps for two weeks my traps provided such minimal additional control and monitoring that I decided to discontinue their routine use. I’ll break them out as only as needed in the future.
You get double bang for your buck using this type of uplight if you have to deal with gnats at all. Once every few days I wipe out the dead ones and polish the reflector.