i think one turbo, 5 nassarius, and 10 other smaller snails (margarita, trocheus, cerith, etc) will be good as far as snails go. these will help keep the sandbed clean and the glass walls/LR clean of diatoms and softer coating type algaes
i think an emerald crab would make a good addition to your tank as well as 10 or so smaller hermits (scarlet reef, dwarf blue, dwarf red, or left handed). this should handle any vallonia (bubble algae), hair algae, and denser tufty type stuff that pops up
they will also all take care of uneaten food
make sureyour nitrites and ammonia are zero and your nitrates are low before introducing