Water is passed through small pieces of carbon or zeolite, which is a natural mineral. The carbon or zeolite remove molecules such as ammonia from the water. Activated carbon, resins, and other adsorbent chemicals bind and remove dissolved particulates from the water column through the process of adsorption. The two most popular forms of chemical material are activated carbon and resins. Protein skimmers, and ozonizers, are two other forms of chemical filtration.
Carbon is filled with microscopic pores that cause 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. Carbon removes many harmful elements from your bait tank, such as copper, chlorine, dissolved proteins, and carbohydrates. It also removes sulfa drugs and antibiotics, so removed it when the tank is being medicated, then replace when treatment is completed to remove any leftover medications.
Ion Exchange Resins
These filter materials are less utilized than carbon, but are becoming more common. They 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 BioChem Zorb.
The resins strengthen the filtering ability of the carbon, as well as help biological activity by removing pollutants before they enter the nitrogen cycle.