I bought a cardinalfish about 2 weeks ago. It took him about a week to start feeling comfortable in my tank and has been very active through yesterday morning. Since then, I haven't been able to find him. He's not floating at the top or down in the sand bed, and I even looked inside the filters to see if he might have somehow gotten inside them. The only other fish in the tank are 3 green reef chromis. Is he hiding out in my live rock somewhere? Or should I expect the worst?