Help Unexpected Babies ? In Local Petshop Buy

[Tu6dolce]

Hello Everyone ,

I am a well experienced freshwater tank hobbyist but new to saltwater.
After weeks of cycling my tank , I purchased from the local pet store yesterday my first snail and hermit crab for the saltwater tank. To my surprise by the time I got home in the bag were also some 50 + babies as well !!! Where did they come from ? Are they baby crabs? Were they in the sand grabbed at the store . There was also a clownfish in the tank they took them from. I am sooo puzzled and dont know how to raise these fry .. Please any advice is appreciated, I will try to send clearer pics.

What do I feed them in the meanwhile?

 

[Donya]

From the pictures I can't really tell what you have. If they came from the sand, then they are more likely to be some sort of other small Crustacean rather than larval versions of your larger inverts. There are lots of little bugs that can ride in from various sources: Copepods, Amphipods, Isopods (particularly Munnid Isopods), and so on. 
 
Even if what you have are larvae from some larger animal, breeding and raising marine inverts like hermits and snails in captivity is pretty much impossible for the average hobbyist. While there are some exceptions to the rule (like Stomatella, for which offspring frequently survive and grow unaided), in general larvae are a lost cause unless you planned for it with a rather specialized setup ahead of time and have a lot of time to devote to the process of feeding and maintaining water quality - which is a constant battle.