Gnat Off contains the shit needed to control them little buggers....
ACTIVE INGREDIENT
Bacillus Thuringiensis subspecies
Israeliensis, Dipteran active toxin(s
Have you been using the Gnat Off per the instructions?
And like sniper said, get some sand and use it now....once you have sand on there use some more Gnat Off.
With D.E. I mix it with the sand before adding to the top of my pots, there is no way I would be putting an inch layer of D.E in a pot as you really don't need that much of it.
You can also mix some D.E in with your medium before planting but you will still be wanting to put a layer of sand on the top.
For Fungus Gnats prevention is way easier than the cure, since you know Gnats are in your area use sand and sticky traps ALL the time and they shouldn't bother you again in future grows.
Stunted Insect
:smokebuds: