Today I came home to find my 2+ year old Royal Gramma in the back of the tank covered in a slime cacoon. He was a goner. He was ~4 inches, very fat & has seemed extremely healthy. I'm not sure what the cause was. I scooped it out of the tank to examine the body, but didn't notice any wounds other than the gills being eaten (which I'm sure the crabs did). I have heard some clicking in my tank occassionally, but a mantis would've either ate him or left some sort of damage...right? I've also seen a large worm (almost 1/4" wide & I saw it going about halfway up the tank with it's body still in the rocks) twice. The worm is white/light tan in color but makes a quick getaway when the light hits it. Water parameters are fine. Any thoughts?