new "things"found in tank!

It's possible that you have baby snails in your tank, but most snails species used in reefkeeping go through a planktonic stage, at which point the adult creatures in your tank eat pretty much all of them. Some genuses do not become planktonic, and therefore are much easier to breed in captivity, though larger creatures will still eat the juveniles, given the chance.

However, there are a lot more types of creatures than just snails that can come on live rock. Any number of crustaceans, hydroids (like jellyfish), and mollusks can hatch out of live rock or live sand and find their way to your glass. Most of the medusas (jellyfish) that hatched in my tank got sucked into the powerheads eventually and chewed up, but my tank is teeming with micro-crustaceans and just had a hatch out of baby snails or sea slugs that have very tiny shells (too small to retreat into). These snails/slugs have a body shape like an upside-down U, with two tiny tails sticking out behind them and tendency to twist around at the center of their foot.