Stocking Issue

Wondering if I'm overstocked, and if not, what are my options for additions.

20g high w/ mechanical filtration (sump shipping next week), 20lb live sand, 15lbs live rock
-2 juvenile clowns
-1 YWG
-1 pistol shrimp
-1 cleaner shrimp
-2 nassarius snails
-4 blue legged hermits