My tank is over two years old and since it was setup I have had two cleaner shrimp and a coral banded shrimp. A month ago my coral banded just "disappeared" from the tank. Then two weeks ago a cleaner shrimp was gone and now today I can't find the remaining cleaner shrimp. I have not heard any clicking sounds of a mantis and have not found any remains of these shrimp. Does anyone out there have any ideas?