Agree with snaps here. If dunks had no effect you just might have the worst pest imaginable. I have them, and they are no joke...
Here is a shot of one of my fungus gnats
Here is a shot of one of my root aphids
The root aphids have wider bodies and their wings extend further behind their bodies. They have less of an hour glass shape. And of course they have the 2 horns or "dual exhaust" on their rear. I won't even try to tell you how to deal with them. They are the devil incarnate! If you want to check to see if you have them put down some duct tape adhesive side up on the floor of your grow in a few different spots. Give it 12-24 hours and check with a magnifier or jewelers loupe.
Here is a shot of what they look like without wings