Activated carbon has been used in home aquariums for decades, and it is still the largest selling filtration media product. As new types of filters and media have become available, the debate has raged over the value of using activated carbon in filters. Some believe it should be used as a standard media for continuous use in most filters. Others feel it should only be used in for special needs, and still others believe that activated carbon should no longer be used at all.

It is important to remember that carbon is exhausted relatively quickly when used in an aquarium filter. For that reason, if the choice is made to use activated carbon on an ongoing basis, it should be replaced regularly. Otherwise, it is of little benefit.

What Is Activated Carbon?

Activated carbon is made from carbonaceous material that has been heat treated at very high temperatures to create many tiny pores, greatly increasing its surface area. These tiny pores and massive surface area allow the filter media to trap a large volume of material, making it useful for removing pollutants from both air and water. Different methods of creating activated carbon result in different forms of the material suitable for different uses. In aquariums, the form mostly used is GAC, or granular activated carbon. Forms of activated carbon include:

• BAC, or bead activated carbon
• EAC, or extruded activated carbon
• GAC, or granular activated carbon
• PAC, or powdered activated carbon (also available in compressed pellet form)

There are also different sources for the carbon itself, each resulting in a different possible pore size. Materials such as coal, coconuts, peat, bamboo, and wood are all used to create activated carbon. For aquariums, the best source is bituminous coal.