Coris can be kinda skittish at first, my red one will dive under the sand if he isnt feeling safe or I start messing with the tank. lol My yellow did the same when I had one in the 90g but my 180g has a yellow coris and he does nothing but swim back and forth all day long. I think he sleeps under the sand but he is almost always out and about.
180g Reef - 60g Rimless Reef -90G FOWLR- 125g Malawi Cichlids- 40b REEF- 34g Fresh Planted-working on- 20L FOWLR- working on
I have a mix of many different saltwater fish amongst my tanks, but I love my Tangs most of all.