Activated Carbon Filter Media

When choosing activated carbon for your tank, match the quantity to your filter's media capacity and your aquarium's volume rather than simply filling the available space, as overpacking can restrict flow while underfilling reduces its effectiveness at clearing discolouration and odours. It's best used as a "polishing" stage alongside mechanical media (such as filter wool or sponge) to trap debris first, and biological media to handle the nitrogen cycle, so water passes through each stage in the right order. Bear in mind that carbon exhausts itself as it absorbs impurities, typically over three to four weeks, so it should be replaced regularly rather than left indefinitely. Freshly cleared, odour-free water is one of the simplest signs of a healthy, well-maintained tank.