Fungas gnats usually appear when the growing medium is too wet. So I'd let it dry out more and not keep it so moist.

In addition, germinate some radish seeds,let the sprouts get long and place them in a moistened dish near your tomato plants to divert the gnats from your tomato seedlings..

Gnats LOVE radish leaves.

Carolyn

Yeah once you encourage a good population to develop they are almost impossible to eradicate. And none of those "home remedies" work.

If you have any Bt in any form it, mixed with water and poured on the soil works. Order Mosquito Dunks on line and you'll get them sooner that going to town.

Fungus gnats aren't automatic, aren't a given, they require certain conditions that WE give them. So you will need to change your watering habits drastically and set up fans in the area to help eliminate them. Alternative transplant your plants into fresh soil and containers that aren't over-watered and pitch all the old potting mix outside.

Dave

Dave's Mosquito Dunks suggestion is a good one. BTi (Bacillus thuringiensis israelensis) is the only thing I have found effective in really getting rid of fungus gnats. BTi is available in Mosquito Dunks, Mosquito Bits, Gnatrol, and Knock Out Gnats. It kills the fungus gnat larvae but is safe for people and pets. If you decide to use the dunks, soak a disk in a gallon of water overnight, then remove the disk and use the water on your plants. Do this every 3-4 days for a few weeks. You can re-use the disks.

Paula