Gerbil Playpen
 

I want to have a sort of "gym class" with my gerbils. Does anyone know what I should use? (paper towel tubes, brown paper bags ect.)

What you can do is get a large plastic box or if you have a small empty room, it would be good too. Just place paper towel tubes, jam jars and old cups, you can even place small boxes around. You can also make a maze by connecting several pieces of cardboards and tubes to make into a maze and let them run.