I haven't seen my diamond watchman goby since I got him it's been 13 days since I placed him in my display tank I saw him swim to the Rock and haven't seen him since. He was drip acclimated I see some moved sand around the back of my tank within the first few days but I haven't seen any more signs of sand being moved around and haven't see him come out once. I've checked my carpet everyday and it has a tight top so he won't jump out. Is it possible he died under the substrate I haven't seen any signs of ammonia or anything. If he did die under the substrate would I see signs of ammonia or nitrites or not until he was dislodged from under the sand like would the sand keep it suppressed? Thanks for any help!