This rotifer is a Brachionus sp. Copepods occur in all aquatic environments. These creatures eat phytoplankton and small microzooplankton. You can see these in this photo. There are other animals with stages called nauplii in addition to copepods, like the barnacle, so not all nauplii are the same.
Ciliates are a group of organisms that are single celled and occur in all aquatic ecosystems.
Unlike the rotifers, they usually have cilia all over their entire bodies. They move their cilia for locomotion and to draw food into their mouth. Tintinnids live in a little home called a lorica. Tintinnids construct their loricas from protein and polysaccharides. Some even add a variety of materials to them such as particles found in the water.