Hey /an/ me and my house mates have a tank, and up until recently its been fine, nothing too fancy, a glass shrimp, a starfish, two hermit crabs, live rock (that we found out was hiding a bristle star and some bristle worms), coral (both living and dead) and a few more shells (that were empty) for the crabs to move into later.

About a week ago we added in a dragon wrasse, it was all good, he was only a young one, still green and white.

The only other thing we were thinking of adding at the moment was a peppermint shrimp, due to a poisonous anemone we have in the tank that we don't want killing the coral.

The other day the dragon wrasse disappeared and, and he hasn't been seen since, worried he might have buried himself and got stuck, but we decided to give him a few days till we pull apart the tank.

One other possibility we are considering (and we are hoping we're wrong) is that there might be a mantis shrimp in there that was hidden in the live rock, or even maybe one of the shells. Reasons is because every now and again we can hear a clicking sound from the tank (but this might just be the filter/heater) and that we found what we thought was a dead hermit crab that had been washed out of the live rock, we were going to get it, but by the time we got round to it several hours later, it was gone. Since the clicking we are worried it may have been the shell of the mantis shrimp.

Ideas/suggestions?