Thanks for the comments!!!! I have 3 moss balls, as I always have had in all my tanks. They are so cool, they roll around the tank, the fish play with them and they also out compete green algae for nutrients. It is actually recommended that you have 10+ moss balls in a 30 Gallon tank. The fish pick the leftover food and detrius off them, and generally have a good play! I would recommend them to anyone with a freshwater tank. As with any algae, with the right conditions they will grow to quite a generous size!
Julia