Fungus gnat. Well first be careful buying soil again from the same place. I never had fungus gnats till I bought from a new store. Two weeks later theres me and three other growers, two I remember from two weeks prior at the store. So I ask one guy...never had em till you bought soil from here? Yes.
I use microb-lift the active ingredient is BT Israeliensis. Bacillus thurigensis Israeliensis (spelling). Predator nematodes work. I even use a neem cake solution to water into the soil at times. Which also works very well for powdery mildew instead of neem oil.
I use more than the 6 drops per 500 gallon rate. A small squirt in 50 gallons or few squirts in the 1000 gallon irrigation tank.
And use a large volume of water, ots not so much how strong you make it, but how saturated you can get the medium with the BTI. And every 3-5 days for a heavy infestation then weekly to keep them down or for prevention.
If indoors you can set dishes with water and sweet scented soap to trap adults.