I was just reading a posting where advice was given that for a 55 gal @ 15 snails was the bare minimum? Is this correct? I have a 75 gal with 6 astrea, 23 nassarius, and 2 large cerith snails. They are doing a great job. Am I under stocked? I also have 6 red leg hermits( really small) and a serpent star that is the sum total of my cleanup crew. What does everyone say?