Little black fruit fly type in GH

I have tomatoes in pots in the GH and suddenly have these tiny black gnat type things in the soil around the plants. I tried garlic and cayenne spray but they seem to keep coming back.Can't identify them in any books. Ideas ?? Solutions?? Thanks guys. Beautiful day here in NE AR.

Could they be fungus gnats? They are a big problem around seedlings but I would think any plant that's a little too wet might run into problems with them. The gnats themselves don't eat the plants, but their larvae will munch on roots. You can use yellow sticky traps to catch the adults, and adding some Bt (Bacillus thuringiensis) next time you water will take care of the larvae (it's the same stuff as Mosquito Dunks, so if you can find some of those that should work too). I've never had fungus gnats unless I've been keeping things a little too wet, so I'd check up on your watering too.