When my house plant collection get these gnats, I allow my soil to really really dry out, about to where you see leaves starting to droop...then water with 50/50 peroxide and water....another method used (that I wouldn't recommend, while in the enclosure) is isopropyl alcohol. Spray the surface soil, and plant down, maybe once a day. Allow soil to dry wayyy out. You can usually tell by lifting the pot, it should be super super light.
You could also remove the plants for a day or two, and leave those sticky traps that are yellow to sit in your pot on the surface of the soil (they come in the shapes of butterflies I believe) this will catch the adults, and emerging larva....but it takes a long time, and has to be repeated. The gnats are attracted to the color, as it resembles dying foliage.
Bottom line, they LOVE moisture...if your in a more humid state, they are harder to get rid of. The key is DRYNESS. if your having an issue with misting and a fogger keep8ng the soil moist, try using clay or terracotta pots they dry out super fast. You can also try a more arid soil, usually sold for aroid plants (my fav.)
If the plant in question is pothos, and your worried about removing it to restart its roots...you shouldn't have to...just "chop & prop" by cutting the sections to desired length then shove directly into the soil and wait, under the warm lights from the enclosure it will root within a week...u can shove the stem all the way to the bottom of the pot if your worried of the cham pulling the vines out...