Heliciculture/Population and Density
Population density also affects successful snail production. Pens should contain no more than six to eight fair-sized snails per square foot, or about four large H. pomatias; or figure one kilogram per square meter (about .2 pounds of snail per square foot), which automatically compensates for the size of the snails. If you want them to breed, best results will occur with not more than eight snails per square meter (.8 snails per square foot). Some sources say that, for H. pomatia to breed, .2 to .4 snails per square foot is the maximum.
Snails tend not to breed when packed too densely or when the slime in the pen accumulates too much. The slime apparently works like a pheromone and suppresses reproduction. On the other hand, snails in groups of about 100 seem to breed better than when only a few snails are confined together. Perhaps they have more potential mates from which to choose. Snails in a densely populated area grow more slowly even when food is abundant, and they also have a higher mortality rate. These snails then become smaller adults who lay fewer clutches of eggs, have fewer eggs per clutch, and the eggs have a lower hatch rate. Smaller adult snails sell for less. Dwarfing is quite common in snail farming and is attributable mainly to rearing conditions rather than heredity factors. Crowding snails is false economy. A recommended rate for H. aspersa is not more than one-third pound per square foot of soil surface for snails that weigh more than 1 gram and not more than .2 pound per square foot for snails that weigh less. (One ounce is about 28 grams.)