Here are two videos I made of Vorticella. These are basically filter feeders. I have posted examples before but these show more detail, especially the vortexes they create near their "mouths" to bring food spiraling in i.e. bacteria, protozoa etc.
Both videos also show their ability to contract the stalk they attach themselves with.
It always amazes me that there can be such complexity on the microscopic scale. The human body is made up of trillions of cells which diversify and make up many different organs, and yet a single celled organism like vorticella still manages to have an internal structure with lots of organ-like structures (organelles).