One is 2 to 4 inches deep and the other is 5 to 6 inches.
If I DO vaccuum, it's only because I have developed cyanobacter or other scourge and only to remove the scourge. Otherwise I let the spaghetti and bristleworms, snails and hermits clean it!
My sand bed varies from 2inches to 5inches. There are hills and valleys throughout the tank. I never vacuum the sand,but I will pull any algae/cyano off by hand. I use HD southdown sand.