The good news is...... Your Soil is alive, otherwise you wont have Gnats
I fight those Foggers in nearly every grow.
You have to fight them in every stage
Eggs and larvaes are in the soil---- the larvaes eat your roots----- Fight them with Nematodes ( Predators)
And then larvaes become lil flies and crawl at the surface of the soil.......
Here you fight them with yellostickers // sticky traps
and you can " seal" the surface of your Growingpots with sand // silica--------- but then you have to water the plants from the bottom
Give always agood airflow---- so the gnatflies can land on the surface... were disturbed when they lay eggs
You can spray the surface with neemoilsolution
You can put blended neemseeds in your Soil
So thats my remedies
And you have to put nematodes in every Growingpot in the house..... even in your regualr plantpots
Then you can get rid of those foggers
and if you mix your soil by yourself... give nematodes in your soilmix from beginning
It takes alittle time.. and you have to pay attention... but its possible