Filtration Systems

All aquariums need some sort of filtration system. In the wild, the ammonia and waste that fish give off are dealt with easily. But in the concentrated and artificial environment of an aquarium, pollutants can accumulate to deadly levels unless filtration methods have been established. There are three aquarium filtration methods available: biological, chemical, and mechanical.

Biological Biological filtration occurs naturally in an aquarium once a nitrogen cycle has been established, but there are also filters available that can enhance the ability of ammonia-neutralizing bacteria to flourish. In reef aquariums (saltwater aquariums that contain live corals and invertebrates), live rock is a good biological filter. Live rock brings bacteria and algae into the organic mix that aid with aquarium filtration. For freshwater aquariums and saltwater aquariums that only contain fish, undergravel filters are often used by beginners. Power filters are a popular alternative for aquariums under 50 gallons, and combine all three filtration methods.

Chemical
Chemical filtration refers to the removal of dissolved wastes from an aquarium. Granular activated carbon is the commonest form of chemical filtration and is suitable for reef tanks and saltwater and freshwater aquariums.

Replace carbon every four to six weeks, using about 1/4 cup for every 10 gallons of water. If you own a reef aquarium, look for low ash carbon to minimize phosphate leaching, or else soak activated carbon for a week or two before introducing it to your aquarium.

In reef tanks or saltwater aquariums, protein skimmers are a valuable method of chemical filtration as they remove organic compounds before they can even turn into ammonia or nitrite compounds.

Mechanical
Mechanical filters remove solid waste from aquarium water. They do not remove dissolved substances from the water. Mechanical filters must be cleaned regularly to be effective. Mechanical filters are also unable to remove trapped wastes, so it will still be necessary to vacuum your aquarium.

Canister filters are a common type of mechanical filter for freshwater and saltwater aquariums. Power filters are another form of mechanical filter. Both canister and power filters sit outside of the aquarium, though canister filters are typically below the tank and sometimes even inside it, while power filters hang on the back.