The filter media baskets can be customized to hold just about anything. You can add chemical, mechanical or biological media.
It's available in four different sizes.
xp1 1 media basket 250 gph
xp2 2 media basket 300 gph
xp3 3 media basket 350 gph
xp4 4 media basket 400 gph
The media baskets of the xp1 though xp3 are interchangeable.