I currently am using an Aqua Tech 10-20 HOB filter and am trying to optimize it before I add more fish(I currently have 5 Black Phantom Tetras). Currently the setup is: Sponge that I added, the filter cartridge that came with it, and the biogrid that came with it. My plan is to replace the filter cartridge with some polyester floss. How do I ensure I'm not removing too much BB by removing the filter cartridge? Or is there enough BB elsewhere?