That's a dandy little grow room. Your girls look very happy there. I think I could be, too.....

I think i heard from somewhere that putting a layer of sand over the dirt will stop the gnats from laying their eggs in your soil...
Weezard said that worked, but was a PIA if you hafta transplant. (Hopefully not an issue here). I've used paper plates with a slot cut to a stalk-hole. Weez has done the same with reflectix--really any barrier to keep the winged adults from laying eggs in the soil.

But my fave is like a buck-two-eighty at Ho-Po:
[attachment=o219050]

Hang them someplace where you're not gonna get yerself caught in it-- like Br'er Rabbit.