There are several different types of filtration that can be used to filter a freshwater aquarium, and the best method will depend on the size of the aquarium, the type of fish and plants that you have, and your personal preferences.

Some common methods of filtration for freshwater aquariums include:

  • Mechanical filtration: This involves using a filter that physically removes particles and debris from the water, such as a sponge or a foam filter. These filters are effective at trapping larger particles, but they may require more frequent cleaning.

  • Chemical filtration: This involves using a filter that uses chemical agents such as activated carbon or zeolite to remove dissolved substances and impurities from the water. Chemical filters can help to remove dissolved toxins, color, and odors from the water.

  • Biological filtration: This involves using a filter that promotes the growth of beneficial bacteria that break down harmful substances such as ammonia and nitrite. Biological filters can be in the form of media, such as bio-balls or ceramic noodles, or the use of a wet/dry filter, that use the bacteria that colonize these media to convert the harmful substances into less harmful nitrate.

  • Protein skimmer: Protein skimmers are often used in marine aquariums but they can also be used in freshwater. They work by creating bubbles that pull proteins, oils and other dissolved organics out of the water.

  • UV sterilizer: This is an electronic device that uses UV radiation to kill microorganisms, parasites and other harmful pathogens in the water. UV sterilizers are effective at controlling harmful microorganisms, but may not be necessary for all freshwater aquariums.

It is important to note that not all filters are created equal, and it's important to choose one that is the right size and type for your aquarium and its inhabitants. In most cases, a combination of different filtration methods can be used.