The ceramic media in your biOrb® forms the main part of filtration 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 in which bacteria can thrive. 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 1/3rd of your media at one time and wait at least a month before replacing any more.