I don't have more than 20 snails and 3 hermits in my biocube 29. Have a variety of snails based on your tanks algae growth. Meaning for me. When I was having heavy diatom outbreak I loaded up on margarita snails to help control that. After awhile the snails died off for various reasons and I added nessarius (3), turbo (8), bumblebees (2), margaritas (5). Combined with the skunk cleaner and the hermits, my tank stays clean.