after several attempts to rid my tank of the few gnats I had I got em! I would see them, take the lid & light off spray w salt water, remove all the food I could see, and wouldn't see them anymore UNTIL I would put the lid & light back on and there they would be. Last night I was so frustrated I yanked that light & lid off, then I figured it out. The little buggers were going in the crack up to light following it when I took the light off! Well they "followed the light" for the last time & now have crossed over to gnat heaven! I have no more bugs! it was like one those ah ha smack your self in the forehead moments, they are attracted to the light so where would they be if not around food?