“Activated carbon” is a catch-all name for products that may be derived from coal, wood, or coconut shell, and which have undergone treatment (“activation”) to increase their porosity; the porosity and average pore size of the material is largely responsible for the effectiveness that it will have with regards to removing dissolved organic material from water and vapor. Contrary to claims made by manufacturers/suppliers of activated carbon, trace and minor elements are both actively- and passively-removed by any quality activated carbon; in the case of the former, this is due to gaps in the pores that are partially blocked by large molecules, into which trace and minor elements can pass and become trapped, and in the case of the latter, this is a result of these elements being trapped in binding sites on the large organic molecules, themselves, which are then removed by the carbon. Therefore, supplementation of trace and minor elements should take place after carbon use. Some hobbyists prefer to utilize activated carbon in their aquaria on a full-time basis, while others choose to employ it only when attempting to remove some sort of undesirable substance, such as an abundance or organic material or a medication. There are arguments to support both methods of use, therefore it is up to each individual hobbyist to determine what will work best for their aquaria. In general, freshwater aquaria, which do not have the benefit of protein skimming, can benefit from full-time use of activated carbon, whereas marine aquaria employing protein skimming may benefit more from only occassional carbon use.