Found this, best read I have found on Gnats.

http://www.ksre.ksu.edu/bookstore/pubs/MF2937.pdf

Thanks for posting this. Yes, interesting read.
says 'Both adults and larvae may spread plant pathogens'. Makes it more damaging than just eating the emerging roots .

Also, it suggests that bottom watering indirectly helping keeping the top less moist and less conducive to the gnat life cycle.

Very interesting article, thanks, it will help me a lot for prevention, not having any problems right now since most of my cuttings arrived healthy. I truly believe that healthy cuttings is the greatest deterrent of gnat infestation, along with Gnatrol drench and pyrethrin spray.

Healthy cuttings equal good roots which equals good eating for the larvae/pupua/worms, kinda like an "eat all you can" BBQ joint.  You got it right with the chemicals controlling or at least trying to control them.

My little sundew collection took care of my problem.

Good read.  Thanks for posting.