Well, I could not resist and bought a pair of ghost shrimp a little while ago and Sir Max's discovery that he had tankmates was interesting!
Max was doing his usual patrol along the length of the tank near the bottom when I noticed him take a turn and head back under a plant very slowly, back where I had seen one of the shrimp under the heater. I peeked around and Max was flared up, his side fins a blur, as he backed the shrimp into the corner, next to the filter intake. Max got close enough to nibble on one of the shrimp's antenna, which caused the shrimp to jump onto the intake cover. Max coasted to where the shrimp had been, and the shrimp then jumped over Max's back and landed behind him.
That's when the other shrimp, who was exploring, came around the corner and joined the chaos. Max turned and now there are *two* new things in his tank. He approached them, they split up, and Max simply swam away, leaving them totally alone.
Now Max is simply patrolling again, passing them and while he can't miss seeing them, he has not made a move towards them since that one nibble, so it looks like my tank is going to be a peaceful place. :)