It is common for certain snails, but I never heard of hermit crab reproducing in captivity. Generally, it is much more difficult to breed crusties like crab and shrimp, because their larvae is planktonic and most will be eaten or filtered out within days if they do reproduce.
I've had a few baby snails appear in the year and few months my tank has been up. They are simultaneous hermaphrodites, so you only need one to make babies. I don't know how commong it is for that to happen, though.
I recently saw one of my apparently female hermit crabs switching shells and she had a clutch of eggs. So reproduction in captivity is possible. I have separated the crab just to see if the eggs hatch at all, but its been over a week already...
my turbo snails mass spawned in my tank on june 16th over here. that's five days before the longest day in england, which indicates some sort of lunar solar cycle. it was amazing to watch with a female at one end of the tank dispersing eggs into the flow and males all around the tank releasing sperm. have'nt seen any babies as of yet but can't wit until i do, will keep u posted....
Yup, I've seen egg clusters on hermits too. As with most crustaceans, they carry these eggs attached to their abdomen until they hatch (relatively long incubation period). They won't survive once hatched though since everything will eat the larvae.
Snails are rabbits It's not uncommon for them to spawn in captivity. Most don't produce any viable offsprings since the young get eaten or filtered, but snails definitely reproduce with relative high frequency. Although most snails are simulatenous hermaphrodites, most don't release sperm and egg at the same time. They have the capability to produce both, but like most simultanenous herms, they don't self-fertilize.
You CAN have your Hermits reproduce if you set up a 10 gallon tank with circulation (mesh over the intake of a power head), using reefwater and low lighting and a lot of cover for the smaller crabs to hide in. They will grow using feed, frozen brine shrimp pulverized and eye dropped in without power head on or with, your call there. Don't overfeed though..DO water changes every 2 days, exactly 10%. Siphon from the top of the tank, not the bottom. Also add some caulerpa if it is available as the babies will graze the algae for planktonic organisms that live on it if you don't have access to FBS.
Aquadoc