Many Fox Farms fans here, but I personally dislike their products, especially their grow mediums. Switched to Coco/Perlite 5 years ago. My current favorite brand is TheBucketCompany coco/perlite ($12.50 per 1.8 cu/ft bag
for now..)
To get rid of fungus gnats, add Spinosad (per directions) to your feed water and into open drains and standing water. They'll be dead within 48 hours if done properly. Also, fill a 5 gal bucket or similar with some water that has a couple tablespoons of sugar or honey in it, add some nice spinosad to that blend too, the adult gnats will go to get a treat and DIE.
I use sticky traps, liquid traps, and UV fan sticky traps near entry points. Bugs get attracted to the UV light, get sucked in the fan, and stuck on sticky paper. Bulk boxes of sticky traps are better than the little disks they sell. Check out this UV trap on Amazon:
https://www.amazon.com/Zapper-Indoor-Sunction-Mosquito-Kitchen/dp/B0C23N2R9P
These are mainly good to place around entry points or commonly infested areas like clone trays etc..