The gnats I faced came from my dumb assembly and cooking of my mix outdoors. I did it all in a kiddie pool probably kept too moist, and by the time I started the grow, the stuff was seriously infested. I knew that, but figured, incorrectly, that DE and BTi would sort the little buggers. The DE and BTi did the job for a while, but not enough to prevent them from coming back.
This time, the mix is assembled from scratch indoors, and is cooking under a cloth lid which will prevent any bugs from getting at it. I will hit it with BTi a couple times before using it, and will do some preventive DE applications as well. I will document my mischief once it gets rolling.
Thanks for the link, I will drop over and have a look.