fungus gnats - sand & Diatomaceous earth

I am out to rid my garden of fungus gnats once and for all. I have been keeping them at bay with a spray for over a year. I intend on using sand & diatomaceous earth on top of the pots. I use coco coir in pots, although its a ebb-flow hydro system, I think it will behave just like really moist soil. I have read about people using a layer of play sand on top of the coco in the pots. I was thinking of using a mix of sand and the dia. earth. Anybody have any experience with this?

I was also thinking of putting some of this stuff


and maybe some of this



Anybody got any tips for me. I am also trying to prevent a spider mite infestation from ever happening.

I use beneficial microorganisms which I get from here that contain
Endomycorrhizal fungi Glomus intraradices,Glomus mosseae, Glomus aggregatum,Glomus clarum, Glomus deserticola, Glomus etunicatum,Gigaspora margarita, Gigaspora brasilianum,Gigaspora monosporum Ectomycorrhizal fungi Rhizopogon villosullus, Rhizopogon luteolus, Rhizopogon amylopogon, Rhizopogon fulvigleba, Pisolithus tinctorius, Laccaria bicolor, Laccaria laccata, Scleroderma cepa, Scleroderma citrinum, Suillus granulatas, Suillus punctatapies Trichoderma Trichoderma harzianum, Trichoderma konigii Beneficial Bacteria Bacillus subtillus, Bacillus licheniformis, Bacillus azotoformans, Bacillus megaterium, Bacillus coagulans, Bacillus pumlis, Bacillus thuringiensis, Bacillus stearothermiphilis, Paenibacillus polymyxa, Paenibacillus durum, Paenibacillus florescence, Paenibacillus gordonae, Azotobacter polymyxa, Azotobacter chroococcum, Sacchromyces cervisiae, Streptomyces griseues, Streptomyces lydicus, Pseudomonas aureofaceans, Deinococcus erythromyxa


I assume the pestside will kill the benificals I add so using them less would be a good thing.

Thanks.