When everyone came home from Christmas break, we adopted a few communal pets on our floor. We have one beta fish, one sucker fish, two goldfish, one "yard fish" which was found last summer in someone's irrigation sprinkler, and two shrimp.
The beta has its own tank, but all of the other fish live in a tank on a table in our fishbowl. We're working on a system to organize who will take care of them.
I've never been a big fan of fish as pets. They are cool to watch, and to write dialog for, but for the most part, they are pretty boring, and gross to clean up after.