There are three types of aquarium filtration which are mechanical, biological, and chemical. Usually, at least two of these processes are used together to help produce a healthy tank.
- Mechanical filtration is the process of removing solid waste products from your aquarium. As the water passes through a filter, solids are filtered out and trapped filter media which can be rinsed and reused or replaced. Mechanical filtration does not improve water quality but may improve water clarity.
- Biological filtration involves the use of a media such as BioMats, BioBalls, BioWheels or specially designed foam to help maintain colonies of beneficial bacteria which break down ammonia. Proper biological filtration can have a large impact on the water quality of your tank.
- Chemical filtration involves using filtration media such as carbon or ammonia chips to help filter out ammonia, odors, and chemical impurities. Water is usually passed through mechanical filtration first to help prevent the chemical filter media from becoming clogged.
There are four basic types of aquarium filters, which are hang on tank, canister, undergravel and wet/dry. All of these types utilize at least two of the filtration processes listed above.
Hang on tank filters are the most widely used. They use an impeller and hold a removable filter cartridge filled with carbon. Some filters have removable sponges, as well as space to hold more chemical and biological filtration media. They come in a variety of styles and some hang on tank filters, such as BioWheels, have biological filtration already built into them. Most types of hang on tank filters are adjustable and allow you to regulate the water flow.
Cannister filters are designed for performance and convenience and are perhaps the most versatile on all the filter types. They offer large capacity filter sections that can hold a variety of media combinations and also allow for higher flow rates. Canister filters are a good choice for larger or heavily stocked aquariums.
Undergravel filters are an effective way to use a heavy gravel bed to trap and breakdown debris and create a home for beneficial bacteria and can be used in in conjunction with other types of filters such as hang on tank and canister. There are two ways to set up an undergravel filter, either with air pumps or with power heads. Both methods allow a draw through the filter plate and create circulation through the gravel bed. Although undergravel filters are a great addition to many tanks, if you choose to include one you will need to use more gravel than normally required and you will also have to perform more frequent water changes to siphon the gravel.
Wet/dry filters are primarily used in saltwater applications and the size of the filter is generally decided by the size of the tank along with personal preference. These filters are generally made of acrylic and have large areas for biological media as well as areas for pumps, heaters, and protein skimmers. Some types can also be fitted for refugiums. Although wet/dry filters can be easily purchased, they can also be handmade from sheets of acrylic or from modified fish tanks.
Once you have decided on the best type of filtration for your tank, the next step is to choose the correct filter media. Some filters, such as the hang on tank styles, have refill filter packs with everything you need to change your filter. Other types of filters, such as canister and wet/dry, allow you to customize your choice of filter media to suit the needs of your tank. For instance, you can buy filter media that can help lower the PH values in your tank; peat moss is the perfect example. Other media, such as ammonia chips, can provide your filter with additional help in breaking down ammonia by absorbing the excess in the water; great for heavy load tanks such as goldfish. Ammonia chips can also be combined with carbon to create another type of filter media.