If you are using Moodle groups, you can change a setting to allow the students in a group to message each other. This gives small groups a private space to communicate. If you add yourself to a group, you can also join the group chat.
Note: you must first set up Moodle groups to enable this function.
How:
Go to 'Participants', click the cog to the right, and select 'Groups'.
Select a group from the box on the left.
Select 'Edit group settings'.
Change 'Group messaging' to 'Yes' (from the default 'No').
Advise students they can now message within their group in Moodle messaging.
Note: If you (the course teacher) want to participate in a group chat, you need to enrol yourself in the group first.