Nematodes. Just do it, and don't fuck with all of the other shit. You can get them off of Amazon for $15. I use them preventatively now so that I don't have to worry about the fuckers. I fought them for almost a year. They will greatly reduce your yields, and mine got so bad that I almost lost some moms. I tried everything that I read about on here, and the only thing that worked were the nematodes. Mosquito dunks, neem oil, cedar oil, azatrol, and so on did not do shit. the nematodes get them in about a week. They also stay in the soil so you don't have to reapply. I use them on my yard as well. They are fantastic little fucks. I love them.
i use diatomacious earth with very transplant and dont have gnats i spread a little on top of soil and then water into soil to cover the surface erea. use a mask to spread because its very fine powder. this can be purchased at any pool supply shop i got a 10 lb box for like 8$ us
https://www.icmag.com/ic/showthread.php?t=42773&highlight=diatomacious+earth
some where around here is a thread by night tiger i cant seem to find