In my reef days, I used everything: ceramic rings and bio balls, lady's hair curlers, even plastic army men in my sumps, all seemed to work. I'm inclined to believe that in most aquariums the nitrogen load isn't so high as to need millions of square inches of surface area for bacteria colonization and even if we had it, it wouldn't all be utilized. In your tank with just snails and shrimp, I wouldn't expect much of a bioload at all. And every grain of sand, pebble of gravel, hardscape, the glass itself and so on will be used by bacteria -plus growing plants are quite good at removing nitrogen. In my own planted tanks, I don't use any bio media. When setting up a new filter, the first thing I do is toss those rings aside. Depending on the tank, I either leave the space empty or replace them with more mechanical media.
Nothing good happens fast in an ecosystem.