[ACBlinky]

Why not turn the tank into a nano reef and add a small, aggressive fish? You could house a frogfish, dottyback, pair of clowns (if you're after attitude, some clowns can be VERY aggressive), Brazilian gramma, Dascyllus damsel, dwarf lion, or hawkfish easily in a tank that size. The only downfall is with many of these fish you won't be able to keep shrimp, and even hermits may become dinner. None of them will bother corals or snails though, so you could still have a beautiful reef.