I have a 115 gallon FOWLR tank. One of the occupiers is a purple firefish. Usually sticks to itself, sometimes will chase a couple of the other tankmates. It usually sleeps under a big shell on the sand. The other day we noticed our chalk goby had moved all the sand from around the shell and we were affraid the firefish waa trapped so we picked up the shell and replaced the sand and the firefish swam away. Ever since, it's been lying in a corner of the tank barely moving. Sometimes it turns, sometimes the anthena is up and othera down. There are no physical signs of anything wrong with it but it's not swimming or floating and it doesn't seem to be eating. It's been 3 days now. Nobody is bothering it. The other fish or shrimp don't really care. I'm at a loss. Please help.