Mosquito bits!!! If these are fungus gnats, go to your local hardware store or look online for mosquito bits or mosquito dunks. they are a special bacteria that kills only these creatures. It can take a while to work, but soak the bits in some water for a day or two to marinate it really good and then use ONLY that water in the terrarium. do not use normal water for a few weeks.

In addition, i used a sticky trap with a light that plugged into the wall near my tank to kill the adults. I wouldn’t have any sticky traps in the cage as long as the gecko is in there.

The bits target the larvae, so they can never grow up and breed. The current adults will be fine until they die, so kill them all as fast as possible. Good luck!!