I am still new to the hobby. I have had a few occasions were fish disappeared with no trace. Last week I added a tailspot blenny. He was adjusting well and eating. He was not picked on form what I could see. I was in the tank trying to fix something about 4 days ago. I knocked down this large rock that is the top of a cave in the middle of the tank. While I was trying to move the rocks back the way there were I did see the blenny, but once I got is set. I did not see it and I have not seen it since that day. Now I am wondering if I trapped it or killed it, I don't know... I was not really going that crazy trying to fix the rocks. I know fish can disappear and hide for a long time, then reappear. It has been my experience with the short time I have been doing this that once they are out of site, they are gone. What do you guys think? I am tempted to move the rocks around, but I am afraid to open up that can of worms again to get them back the way they were.