well now I'm not sure if my XP2 has any bio media in it. It has 4 foam pads and a white pad. I don't know if bacteria will grow on that stuff?
I wonder if I need to get this:
Bio-Chem Stars® - for fresh and salt water
• Grows massive colonies of beneficial bacteria
• Provides more growing area than plastic balls, foams or undergravel filters
• Advanced polymer material has optimal pore size for maximum oxygen and water transfer
• 20 stars support up to a 100 U.S. gallon (379 L) aquarium
???