Will this work against fungus gnats?

Instead of a sand layer, does vermiculite work as well?

Sand works but I use those fly strips which seems to work quite well.Haven't seen any of those buggers since I started using them.

thnx but doesnt really answer my question.

Legal, I read on a website the suggest putting a layer of perlite on top of the soil an inch or 2 thick, so vermiculite probably works as well. I just got back from the hardware store with some neem oil and yellow sticky traps. I sprayed the soil good with neem oil and couldn't see any movement anymore, I layed the sticky traps down and we'll see if any appear. It's just something you gotta monitor, I'm assuming. I hope you find something that works for you!