I've had an engineer goby for years now. He's always stayed burrowed under rocks, just peeking his head out to grab food. However, I moved the rockwork around a couple days ago and since then he hasn't found a burrow again. He's now spending all of his time either out on the sandbed or even frantically swimming around near the top of the tank. I'm worried this might be severely stressing him out. I did pile some rocks in an attempt to give him an inviting spot to hide, but so far no interest. Any suggestions?