Activated Carbon and Chemical Filtration Media Explained

Most filters combine three types of filtration: mechanical (trapping debris), biological (housing bacteria), and chemical (removing dissolved substances) — activated carbon is the most common chemical media.

What Activated Carbon Removes

Carbon adsorbs dissolved organic compounds, discoloration, and odors, helping keep water clear and fresh-smelling between water changes.

When to Use It

Carbon is especially useful after medicating a tank, since it can help remove residual medication once treatment is complete, and generally useful for maintaining clear, odor-free water.

When to Avoid It

Remove carbon before dosing certain medications, since it will also remove the medication itself, undermining treatment. Some specialty additives, like certain coral supplements, are also affected by active carbon.

Other Chemical Media

Products like Purigen work similarly to carbon but with different absorption properties, and phosphate-removing resins are popular in reef tanks specifically to control nuisance algae fueled by excess phosphate.

Browse filter media options in our aquarium accessories category.