Just got a firetail goby a few days ago and today I woke up and saw nothing but my clown and my hermit crab in my tank. It's only a 12 gallon tank so the firetail couldn't have gone far. I finally noticed the smallest bit of its tail sticking out of the bottom of the only rock I have in the tank. It has managed to wedge itself in between the rock and the bed of sand. Anyone know why it is doing this? Thanks.