Another option (that I used and it worked beautifully) is ladybugs… This was before I switched to coco though. I had a ridiculous infestation of fungus gnats. I dumped this bag of live ladybugs in there and they ate tf out of them in a week.
By infestation, I mean I had to wear a mask to open the tent or I would inhale several of them. It was bad and this worked very well.

I was one of the first guys that got that new Phyto-Max 3 light 










