This activity is very common at professional conferences and can work well in the classroom as well. The premise is that a small-group discussion is more meaningful than a large-group discussion. Additionally, fishbowls blur the lines between speakers and audience, as everyone gets a chance to be both.

The entire class is sitting in 2 or 3 concentric circles, whereby:

• the inner circle (3-6 people) discusses  the topic at hand — the speakers
• the next, larger circle, listens to the conversation without interrupting — the observers
• optionally, a third circle can serve as notetakers. — the synthesizers.

You serve as moderator and give the speakers a topic of discussion.

The conversation is limited to a short amount of time (5-20 minutes, based on your need/topics, time available, and group size).

• In an open fishbowl, a speaker seat is open to allow someone from the listening circle to join in. When this happens, a speaker voluntarily gives up his/her seat, so another audience member can join.
• In a closed fishbowl, all seats are occupied by speakers.

When the discussion reaches the end of the time limit, the moderator summarizes what was said and then, time permitting, invites another group to come to the inner circle, while the previous group sits in the listening circle. You can rotate until the entire class had a chance to be in the inner circle.

For more details and ideas, refer to this article from Facing History and Ourselves.