Oh damn, you need to be
real careful with watering them large pots and maybe even need to dry out your soil to make the larvae in there die and make a trap to catch the adult bastards, I would definitely try something like this:
"Pour one-quarter to one-half inch of apple cider vinegar into a clear or semi-opaque plastic cup, creating an effective fungus gnat trap. Add a drop or two of liquid dish soap and stir to combine thoroughly. Cover the top of the cup with transparent tape, leaving a one-eighth-inch opening in the center of the taped area.
Fungus gnats are lighter than liquid, so they’re able to walk across the surface without sinking. Dish soap breaks the surface tension of the liquid, causing them to drown in the vinegar in the trap.
Drop a small bit of ripe fruit such as banana or cantaloupe into the vinegar. Make sure the bait is large enough to protrude above the surface of the liquid. It will attract adult gnats faster than vinegar alone.
Place the vinegar trap near your plants and check it daily. Don’t disturb it if you see gnats congregating on top of the taped area; they’ll soon find their way into the hole and down to the vinegar.
Set up some yellow sticky traps around your plants to attract hovering adults to the area.
Cut a fresh raw potato into chunks. Place a few pieces on the plant’s soil for two or three days. Pick up the potato pieces and look to see if anything has been chewing on them. No bitemarks means gnats population gone..