Adult fungus gnats. The female lays eggs in moist, peaty potting medium and the larvae either feed on the peat or other organic components or on the roots of seedlings.

Along with some cultural changes like adding fans, allowing the medium to dry out a bit, and changing the consistency of your potting medium the next time, you can try Bacillus thuringiensis Israelensis, a naturally occurring biological control for fungus gnats (and some other members of the same insect order). Bt-i can be found as Gnatrol or you can purchase plain old mosquito dunks (a mosquito larvaecide) to soak in your watering containers. Bt-i products need to be used whenever you water (not more often) for three or so weeks.

You can also use sticky traps to catch the adults.

Your seedlings look like they sure need some better light! When are they going to be placed in some real sunlight?

Mix 1/2 cup Vodka and 1 1/2 cups water in a 16 oz trigger spray bottle and spray on the plant in the coolest part of the day.
Can use on house plants too.
Before spraying this on the whole plant, test it on one leaf to make sure it won't burn the plant.
This should kill your gnats.
Do not use it on African Violet's or tender plants like that.

I tried letting the soil dry out for a few days before. But my plants didn't seem to like that. I'll have to find some Gnatrol or mosquito dunk.

I know. I really need to move them. I never thought they would grow to be this big. I need bigger pots. But that cost money and I'm a poor college student!

Thanks for your help.

Vodka? Will it work on whiteflies on my mint? If it sounds too good to be true, is it?