Latin names for some the more common snails: Pomacea Bridgesii, Pomacea Canaliculata, Marisa Cornuarietis, Vivaparidae (to name a few)
Origin: Various locations world-wide (most Apple Snails are tropical)
Temperature: Variable, but for the tropical variant 18 to 28ºC (65 to 82ºF)
Agressivness: Most are very harmless, although the P.Canaliculata has been known to be semi-aggressive with slower moving species of aquatic animals esp. when food availability is low.
Size: Variable; the smaller Viv's remain quite small (some adults may be as small as 2 to 4 cm), while P.Bridgesii sp. Apple's may top out at about golf ball size and adult P.Canaliculata may top out at soft-ball size.
Tank Size: In the case of aquatic snails, tank size isn't quite as important as filtration capabilities. I've kept snails in 10 gallon tanks, but the filter used on the tank needed to be twice the recommended size to accomodate the amount of waste that snails produce. I keep about 3 dozen adults in a 55 gallon tank, but I run two HOB filters that are "turning the water volume over" approx. 15 times per hour. (Snails produce a LOT of waste)
Food: Vivaparidae sp. do well in a planted tank as they mostly feed on soft algaes. P.Bridgesii have been known to starve to death in densely planted tanks when food was not provided (they lose their appetite for algae as they grow into adulthood). They should be provided calcium rich aquatic animal foods for optimum development of the shells (as should any aquatic snail). P.Canaliculata and Marisa C. species have voracious appetites for just about any type of vegetation (vegetables and/or aquatic plants are definitely on the menu), but should also be provided calcium rich prepared aquatic animal foods.
The short list of foods that I try to make available to snails is: aquatic turtle pellets, crab & lobster granules, shrimp pellets, earthworm flake food, spirulina pellets and/or flakes, variety wafers, algae wafers (for those snails that appreciate them) and foods prepared for omnivores that contain calcium high on the ingredients list (because they are listed in order of predominance). I also supplement calcium in my tank in the form of processed chicken egg shells (see comments for processing instructions), liquid calcium (I have a definite brand preference) and iodine supplements. I use the shells of approximately 12 eggs weekly in my 55 gallon tank. I use 1/4 tsp. of liquid calcium daily and 5 drops of iodine twice a week. *Note: Remember I'm treating 55 gallons of water containing approx. 3 doz. adult snails.
Spawning: Viv's give live birth to babies. Eggs are deposited inside the opening of the shell and hatch (usually a few at a time) fully aquatic. Marisa C. lay aquatic eggs that are clear until the embryo begin to develope (at which time they begin to darken). P.Bridgesii & P. Canaliculata lay aerial calcareous egg clutches (above the water line). P.Bridgesii clutches contain between 50 to 200 egg cells and are pinkish beige (almost skin color). P.Canaliculata clutches contain between 50 to 200 egg cells and are bright pink/orange in color (almost flourescent...very bright in contrast to P.Bridgesii eggs).
Processing Egg Shells for Calcium: Wash shells in hot water. Collect an amount that will be "worth" processing (I use an old metal bread pan to collect the shells in). Bake in the oven at 350ºF for about 15 mins. Remove and let cool. Place in a coffee grinder or in a ziploc baggie. If using ziploc baggie method, I use a wooden rolling pin to roll and roll over them until they are crushed to about the same particle size as large particle (blasting) sand. Turn off your filter and pour the shells into the water allowing them to settle into the substrate before turning the filter back on (this is esp. important if you use the type of filter with magnetic impeller assembly as the shells will get in the assembly and "score" (damage) your assembly).