Teeny-tiny bugs in humidity saucers

[justatypn]

Oh my gosh, I feel like the pest and disease child today. Once again during my maintenance routine, I filled my peeble rock filled saucers when watering my chids. Dang if I didn't see little little teeny-tiny bugs, white or gray in color running around. I am sure that they are not just there to sunbath so I am assuming they might be in the medium as well. Any ideas on how and what I can use to get rid of them.