Shamus, my newest guy, is somewhat of a bottom feeder, always searching. Ted, the older one, absolutely refuses to chase fallen food. I dropped a new rock (very cool, looks like a footprint-the size of about 2 lima beans) in Shamus's tank, he swam across the tank from it then began to approach it very, very slowly. As he got closer he got all sideways, like a cat, and stared it down.
This afternoon I placed the carbon monoxide detector on the table next to his tank so I would remember to buy a battery for it. He has flared at that think on and off for about 3 hours until I moved it.