Creatures from my LR

Hello every one. Im new to the site and i have some questions about some creatures I recently found in my tank. I have a 75 gallon tank that has been set up for about a year now. One eel about 8" long, two emerald crabs, and one brittle starfish. I live at school for most of the year and my tank is at home, so i cant really have anything that requirs too much care until i graduate.
I was recently staring at my tank and noticed several pearl white snails. the biggest one was was about the size of my thumb nail and the smaller ones were really tiny. I'v never purchased a snail and i'v seen about half a dozen of these little guys crawlin around.
I have also found some little mites that crawl around. I flipped over a piece of rock today and there was a bunch of them hiding under there and they all scatered. they look like tiny sand mites.
Is it common to pick up live critters like this from LR? could they be dangerous to my tank?

 

mites are probably copods jmo

 

Hello and Welcome to 3reef,

Sounds like the normal hitch-hikers. Copepods and amphipods. If you look at this link it will show the usual suspects as far as hitch-hikers go.

Live Rock Hitch Hikers

 

thanks corailline, that site helped out a lot. its amazing all the different things you can discover from your LR. its like playing the lotery with rocks. you never know what you might come home with.
;D