I was also plagued by earthworms - dozens in the pool every morning. Along with mole crickets, grasshoppers, june bugs, spiders, ants, and other associated insects. I finally got completely fed up and put out a heavy dose of lawn insect killer - turned out be one of the best ideas I've had this summer. I used to get moles digging tunnels underground and armadillos digging holes everywhere. Since I put out the insecticide I haven't had any of those problems.