After searching for crazy in my Biotope (wife helped as well with a flashlight in the dark) the last couple of days for my Amano shrimp, I finally found one. The thing is, he stood on the little submerged flower pot presenting himself in all his glory for two minutes and then scuttled under a plant. I could swear he turned invisable becuase one second he was there and then he merged into the background. The guy at our LFS said he had many people telling him that their shrimp were gone but they turned up again a couple of weeks later!