I have a dedicated cherry red shrimp tank that I cull for less colorful shrimp every few weeks. These less colorful shrimp go into a tank with white mountain minnows and celestial pearl danios. I generally see 20 or more culled shrimp at any one time in this tank. However, lately I only see one or two at any given moment. There are no dead bodies on the substrate. I have never seen the fish in this tank attack and eat the shrimp. My dedicated cherry red shrimp tank is thriving. Any ideas about the collapse of the population?