Chemical media
Chemical media is not used as often as biological or mechanical media, but can be effective for an assortment of filtering purposes. This media is available in a variety of materials that can remove one impurity or many.
The chemical method of filtration removes dissolved particulates from the aquarium via activated carbons, resins, and other adsorbents. Chemical filtration media helps to maintain water quality as unwanted dissolved matter adheres to it. The two most popular forms of chemical media are activated carbon and resins. Protein foam skimming or oxidation with ozone are two other forms of chemical filtration.
Activated carbon
Carbon is filled with microscopic pores that allow certain organic or inorganic materials to stick to them. New carbon works more efficiently than older carbon. When all of the pores are filled, the carbon is no longer effective and the filter begins to act as a biological filter.
Carbon removes many harmful elements from your aquarium, such as: copper, chlorine, dissolved proteins, and carbohydrates. It also removes sulfa drugs and antibiotics, so it should be removed when the aquarium is being treated, then replaced when treatment is completed to remove any leftover medications. Activated carbon can make your aquarium look so clear by removing discolorants that you will question whether water is still in it.
Ion exchange resins
Resins are less utilized than carbon, but are becoming more common. These work by attracting a specific molecule to adhere to them. Some attract ammonia or nitrate, and some remove dissolved organics. Ion exchange resins are also utilized in some carbon mixtures like Chemi-Pure and Bio Chem Zorb. The resins often strengthen the filtering ability of the carbon, as well as help biological activity by removing pollutants before they enter the nitrogen cycle. Used properly, chemical filtration can be one of the most useful tools of the aquarist.
Summary
When designing your aquarium, give careful consideration to the types of filters and filter media you will use. Your choices can make the difference between a healthy ecosystem or one in which the inhabitants must struggle daily to survive.
