When it comes to filtration processes, there are three kinds that are normally found in aquariums. These are mechanical, then biological and chemical filtration. Generally, aquariums should have at least two in place - mechanical, then either one of the other two. For bigger aquariums, a combination of all three usually works the best.
When it comes to chemical filtration, carbon is often used as a filter media because it can effectively remove chemical impurities and contaminants through a process called adsorption, which involves the adhesion of particles of a substance to the surface of another substance. In the case of carbon, unwanted materials adhere themselves to its surface easily and quickly.
Given how carbon works when used as a filter media, it's easy to see that it accumulates dirt over time. Thus, carbon filter media should be replaced regularly. If you are using a 501 filter from Zoo Med, you can replace your carbon filter media by buying the Zoo Med Carbon for 501 Filter from Pet Store.
This product should replace saturated and exhausted carbon filter media in your 501 Filter. The Zoo Med Carbon for 501 Filter ensures that the chemical filtration process within your aquarium is always efficient and effective.
Carbon replacement for 501 filter