I can't remember the last time I had a totally gnat free grow. I'll get a stretch after bombing and bleaching, but they always come back. I use a standard fly strip, and I have a run-off catch tub and I'll leave water in it between waterings. It keeps them in check, but never gets rid of them totally. Benificial soil bugs are the only thing that will kill them. I've heard that a cap of fine play sand will keep the adults from getting out of the soil or coco and end the reproductive cycle, I've never tried it, just read about it.
The grow looks really good, I follow the ML principle, but only so far, I just don't have the patience to follow it to the letter. lol