Beneficial Bacteria live on the highly porous ceramic media. This biological filtration converts the waste produced by the fish and ensures that the aquarium remains a healthy environment. All biOrb aquariums are supplied with ample ceramic media, however, extra ceramic media can be added to your biOrb aquarium. This will increase the area available for biological filtration and makes it easier to anchor plants into position. Over years the micro holes in the ceramic media can become clogged so replacing some may be beneficial. If you wish to change the media you should do so gradually, in stages, and not all at once. Changing the media gradually allows the existing filter bacteria to move across and colonise the new media from the old.