Garden Pests and Diseases: Gnat Larvae Growing in Sand??, 1 by Snug_As_Bug_Rug

Snug_As_Bug_Rug wrote:
The fungus gnats seem to have overtaken my indoor plants. I have provided a photo of my Olive Tree, which I thought would be low maintenance. I've tried everthing from watering my plants from below to dry out the soil surface above, bug sprays, Neem oil spray, and finally I even tried removing the top layer of soil and adding new fresh soil, and then applyiing a thick layer of sand. And now they seem to be growing in the sand. See the larvae in my pic. I thought gnats multiply in wet, overwatered plants?

Also, after I dried out my indoor plants (without killing them), then the spider mites appeared on some. I also placed Bounce fabric sheets to repel them too, and still they return. (see: http://www.sciencedaily.com/releases/2010/12/101215102308.ht...

What am I doing wrong?