I like to watch them too. My best "showings" seem to be when I kill the pumps for 20 minutes to feed (I do smaller feelings twice, and a big one without flow after work). Idk if they smell the food, or it's just easier to tell the smaller ones from other floaties in the water when it's still, but I woulda never thought there was so much going on.
Barnacles are my favorite, they show up once in a while but they don't ever stick around long.
Also, all different critters at night. Red light bulbs are cheap and show a whole nother world in the tank. I heard you can use your phone to shine a red light but haven't tried it.