well jjman, I wish you luck with your Mandarin goby. Beautiful fish but they just don't last in a new or little rock tank. How long have you had the little guy? I suspect no more the 3 or 4 months. The poor guy will die before you have had him 1 year. Even if you focus on his feeding he will parish. I don't want to discourage you but hey been there and my point is..is it worth it. Good luck I hope you prove me wrong