Idk. I tried dia tinaciuo earth (that is not spelled right) but when you top feed, well it turns to shit in one feeding! Sand may drain better, but I prefer hydroton. need something to dry out the top layer, where they lay their eggs.
I found this site helpful
http://www.growweedeasy.com/fungus-gnats
Well Ive only seen a few in the tent and squashed the little bastards. Put yellow stick pads in there and cant see anymore might get some of those pebbles!
Thanks for the reply man