Another idea for the activity I have is about dipping and treating corals and fish. Maybe a show and tell for what to get or keep on hand in terms of medications, etc.
If more people are fragging and trading frags, they really should know about the parasites and disease that can spread through trading and how to treat for them. Some of the nasty bugs can wipe our your entire collection of zoanthids, SPS's or another type of corals.
Tomoko