indoor plants have gnats - help?

[tropicana]

i know it's my fault, i overwater. i have upwards of 90 plants spread out over three areas of our upstairs. they get great sun! only one room has gnats. i've looked online and see that "saturating" plants is culprit. there is also a stinky smell.

trouble is some of these plants *like* ample water. the leaves dry out when i don't water well. i do believe that these are the only plants with the gnats (and the smell). 

is there any other solution to the gnats? to get rid of them?

if i do let them dry out some, how soon will the gnats go away?

thanks for any advice.

[Buzzer Beater]

I used this for fungus gnats:

http://www.planetnatural.com/site/beneficial-nematodes.html

It's an investment, but they work. Don't use them if you are going to dry the soil out tho.

If your soil smells funny I think I'd repot first, then add the nematodes and be vigilant on a watering schedule.