gnats come free with evey bag of "organic" soil mix. unless its been sterylized. what timing! i just transplanted 5 gods into one gallons, with the new pro mix hp. it looks nice. and its supposedly sterile. however, this soil has no nutes in it. its all up to me. but i got tired of cooking my soil, to avoid gnats. i was using a product called "gognats". its cedar oil. i watered in with this, when transplanting. even cooking the soil did not get all of em. i had yellow stickiys, and the proof was on em. a few here and there. also, you can use 3% peroxide mixed in the water, and that helps. but, after leaning all this, im now simply "avoiding them". with a steril soil. if gnats can be in soil, so can worse things. i will say this. in over three years, gnats are all i have had. other than an occasionl "chewer", which is obviously not an issue. he needs to eat to. i think its a potatoe bug. lol. hope this helps. im not much more than a newbie even now, but i try to help.