diatomaceous earth aint gonna help ya with hydro pests, I don't think ... I could be wrong, naturally ... I understand the DE works, by having microscopically-small sharp edges (it's decomposed seashells, etc) that slices the bellies of some bugs that crawl thru it (ouch) :wtf: it wouldn't do anything to flying insects ... when exposed to moisture, it turns to a fine mud. pretty messy ... usually used as a filtering agent, and to make 'latex' paint ... :smokin: