As you add fish and feed more, you'll end up w/a lot more hermits - up to maybe 70 - 100 of'm IMO
. There's probably enuf pickin's on the rock for at least 25 or so now. You'd probably only rarely see 2 or 3.
Also, cleaner shrimp clean tanks of leftover food and fish, so add 3 of them to your ultimate list (once you've got the water pretty stable). Maybe a couple fire shrimp for color also. May need some sinking food to keep'm going. Mix up the snails. Astreas, ceriths, margaritas for the rock and glass. Nassarius for the sand bed. Up to 100 anails eventually won't be out of your range either. Consider a brittle or serpent starfish. I also like the pistol shrimp and shrimp goby (plenty variteies to choose from), but you've gotta have your rock planted on the bottom glass to prevent toppling when they tunnel thru the sand.