Fungus Gnat infestation

Hello. You said "crawling on the surface" is that the soil or the plant or both? A photo would help😊. You have to order nematodes from a garden center and they will take care of any pests in the soil. Sprinkle a little cinnamon around the plant, it kills the fungus the gnats live on and they don't come back.. Please look up cinnamon for plants there's lots of other uses for it. And then there's always diatomaceous earth. If the plant is in veg you can put some in a spray bottle and apply to the leaves. Makes a hostel environment for all insects. Have you tried Pyrethrin insecticide power. Very safe to use. Put right on the soil or put it in the spray bottle too. Insecticidal soaps only work if they come in contact with the pest. Please don't use neem oil, it was banned in Canada for a reason, the heavy metals in it were being smoked some how and making people sick, Imagine that😬. There I've given you somethings to look up and see what would work best for you. Chuck.

If they are white it still could be beneficial soil mites. Yet a picture could tell. Soil mites are my friends not my enemies. Yet gnats.. i luckily never have a bad pest. As suggested might use neem oil

Some of the Safers products are good for multiple problems. I’ve been fighting a mild case of spider mites and it’s working for me.

Like Mooncat said in the previous question you made. Neem oil works, I’ve used some Safers Insecticidal soap. I would try those yellow sticky traps. Trapped ones can’t lay eggs everywhere. But definitely drain that medium and let it dry. Ummm in the future add a bit of perlite to your soil so it can drain an bit better between waterings.