After 4 days of running the tank, I found little critters roaming around the tank. After staring at each of the live rock, I notice something moving. I got closer to the rock and notice that there were 2 snails working away. They were very small; a little over a quarter inch in diameter. Above the two snails on the back glass, I also notice something else. There was a starfish on the wall of the tank. There are good and bad things when it comes to hitch hiking. Some of the bad things could include aiptasia, parasites, dead organisms, etc. Some of the good things could include copepods, amphipods, feather dusters, starfish, snails and other microorganisms.