interesting thread. I just started a saltwater tank and have something wierd living in my live rock. it lives in a small hole that goes back into the rock about an inch, and during the day I will find this brown stuff coming out of the hole. It does not look silt, more like fish poop, but I don't have any fish or inverts in the tank yet. when I got rid of the stuff the first few times I saw it, I saw something move back into the rock, but I could not see it well. I am thinking some type of worm, I hope it's nt harmful. any ideas? I am really new at saltwater, thanks for the help!