Aquarium Filters


Aquariums are closed systems. What goes in the aquarium stays in until it is removed. Fish produce waste and corals emit toxins that pollute the water. While water changes help a lot, fish tank filters are the aquarium’s life support system. Aquarium filters are exactly what they sound like; they filter aquarium water by removing harmful waste and chemicals. An aquarium filter also circulates water, keeping the tank oxygenated.

Aquarium filters use various methods to keep the water clean. A biological filter creates a place for beneficial bacteria to thrive. Through a multi-stage process, bacteria transform toxic ammonia from fish waste into harmless nitrogen. A fluidized bed filter can be a type of biological filter. A mechanical filter traps debris so it can be removed. Take, for example, a filter pad or sponge that captures uneaten food. A chemical filter, like carbon, uses filter media to remove waste and toxins. The best aquarium filter will employ multiple types of filtration to keep your reef tank clean.

If you are looking for the best freshwater aquarium filter, there are many great options. For tanks less than 30 gallons, a power filter works well. Freshwater tanks up to 150 gallons can really thrive with a canister filter. For a large freshwater tank (over 100 gallons) a wet/dry filter is a great choice.

Saltwater aquarium filters differ from freshwater aquarium filter systems. The most important saltwater aquarium filter is the protein skimmer. But, saltwater hobbyists use multiple types of aquarium filters to maintain the pristine water their tank inhabitants require. Media reactors can help provide minerals for growing corals, remove organic waste or reduce algae-causing phosphates.

Want to know which are the best aquarium filters for your tank? Be sure to read the aquarium filter reviews from other aquarists on our website! Have questions about fish aquarium filters? Contact our experts if you need help shopping for an aquarium filter.

To learn more about aquarium filters, read Filters and Filter Media for Saltwater Aquariums, Reef It Simple, Part 2: Let's Talk Filtration, How to Plumb an Aquarium Sump or Wet/Dry Filter System, How to Set Up a Refugium or reference our How a Sump Works infographic.