Hey Growmie,
There are actually a few other things that you can try that are effective, like :
Yellow sticky traps
Get yellow sticky traps from the garden store and position them around your plants. These traps attract the fungus gnats, which will stick to them. Know that yellow traps alone will not entirely eradicate an infestation. But, they are a good indicator of whether you (still) have fungus gnats and can prevent many of them from harassing your soil.
Neem oil
If you have a pest infestation, you donāt need to get all hardcore with chemical insecticides. Neem oil can help get your infestation under control. Itās also good as a preventative measure. Treat the top layer of your soil with it to eliminate the larvae.
Blow air over the soil
A simple standing fan gently blowing air across your soil has lots of advantages. Making life miserable for bugs is one of them. It will also help dry out the soil quicker to eliminate the gnats for good.
BT bacteria
Some growers know the Bacillus thuringiensis bacteria for getting rid of caterpillars. There is a variety of these bacteria, Bacillus thuringiensis israelensis, that works for fungus gnats. Just add water.
Hopefully, I answered your question and remember Happy Growing and Free your mind one puff at a time.