I use spectracide immunox 3 in 1 to control them in my system. I spray liberally when I see them flying around. I think you have to saturate the medium to make sure any larva or whatever is killed. I spray any I see then saturate the medium around where they are flying.

BT will kill fungus gnat larvae.

Sprinkle it on the plant.

Hi
gnats suck and are hard to get rid of
Hydro wont help either, it wont make things worse unless your plants are unhealthy
The problem with these bugs is that most likely they show up in unhealthy plants, so you may want to check for dead or dying parts of your plant including roots and especially the base.
Use those sticky traps or other natural things I had pretty good result with cigarette tobacco soaked in a gallon of water misted and watered with it for about a week

I use a canvas or mat from kisshydroponics.com and PJ it is passive and easy. ck it out in the web. I had a super infestation but with help from kiss they are gone a do not come back. truly it is so cool just cut this mat and place it around the trunk of the plant, it has tiny holes. the gnat can't get through and get its head stuck and dies, so passive but if you have a bad one then read what to do small amount of PJ spread on the mat, follow directions, and they are gone.
maintenance with mat and cedar oil is soo cool and sooo nice to smell in the plant room.
kisshydroponics.com help me

Here is a link that might be useful: kisshydroponics

z1rckelle
What a nice commercial, did you get paid for it?????? Or is it your website and your just promoting yourself?????????