biOrb Ceramic Media is the biological part of the filtration process – as the aquarium cycles, the media slowly gets populated with beneficial bacteria, which makes your aquarium easier to care for. The biOrb Ceramic Media forms the main part of filtration in your biOrb and is important in keeping the water clear and healthy. Beneficial bacteria colonize the ceramic media and remove toxic fish waste from the water as the water flows through it. biOrb Ceramic Media is full of pores for bacteria to live in; just 2 pounds / 900 grams of ceramic media has the surface area equivalent to a soccer field. You can add more media to your biOrb to increase the area for filtration. Over time, these pores can become blocked with dirt and limescale reducing the surface area available. Replacing some of the media every year or so can help to keep the filtration efficient. Never replace more than one third of your media at one time and wait at least a month before replacing any more. Available in a two pound bag.