For cleaning the sand bed I use Fighting conch, Queen conch, cerith snails, Nassarius snails, and Tigertail cucumbers. I wouldnt recommend the Queen conch they were sold to me incorrectly labeled and get way too big for the average tank.
For cleaning the glass and LR primarily columbellid grazer snails ( sold by IPSF as Strombus grazer ) They breed in the tank very successfully. Look for species of trochid, check and be certain the snails you buy are tropical, many sold in the hobby are actually temperate species and dont do well long term.